subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro git-subtree-mainline: 464bbcb15c git-subtree-split: 24f5a642af Change-Id: I6105b3762b79126b3488359c95978cadb3efa789
2021-12-14 01:51:19 +03:00 · 2021-12-14 01:51:19 +03:00 · 019f8fd211
commit 019f8fd211
parent 464bbcb15c 6123e97692
766 changed files with 175420 additions and 0 deletions
--- a/users/wpcarro/website/sandbox/contentful/.envrc
+++ b/users/wpcarro/website/sandbox/contentful/.envrc
@ -0,0 +1,4 @@
+source_up
+use_nix
+export CONTENTFUL_SPACE_ID="$(jq -j '.contentful | .spaceId' < ~/briefcase/secrets.json)"
+export CONTENTFUL_ACCESS_TOKEN="$(jq -j '.contentful | .accessToken' < ~/briefcase/secrets.json)"
--- a/users/wpcarro/website/sandbox/contentful/.gitignore
+++ b/users/wpcarro/website/sandbox/contentful/.gitignore
@ -0,0 +1,2 @@
+.cache
+dist
--- a/users/wpcarro/website/sandbox/contentful/README.md
+++ b/users/wpcarro/website/sandbox/contentful/README.md
@ -0,0 +1,18 @@
+# Contentful
+
+I have not used a CMS in a few years. I learned about Contentful from a
+Gatsby.js tutorial, and I wanted to learn more; I created a Contentful account,
+and I'm experimenting with the data here.
+
+## Developing
+
+```shell
+$ nix-shell
+$ yarn run dev
+```
+
+## Building
+
+```shell
+$ nix-build
+```
--- a/users/wpcarro/website/sandbox/contentful/default.nix
+++ b/users/wpcarro/website/sandbox/contentful/default.nix
@ -0,0 +1,19 @@
+{ pkgs, ... }:
+
+pkgs.stdenv.mkDerivation {
+  name = "ideal-website";
+  src = builtins.path { path = ./.; name = "contentful"; };
+  buildInputs = with pkgs; [
+    nodejs
+    # Exposes lscpu for parcel.js
+    utillinux
+  ];
+  # parcel.js needs number of CPUs
+  PARCEL_WORKERS = "1";
+  buildPhase = ''
+    npx parcel build index.html
+  '';
+  installPhase = ''
+    mv dist $out
+  '';
+}
--- a/users/wpcarro/website/sandbox/contentful/package.json
+++ b/users/wpcarro/website/sandbox/contentful/package.json
@ -0,0 +1,26 @@
+{
+  "name": "tailwindcss",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "dev": "npx parcel src/index.html & npx tsc --watch --noEmit"
+  },
+  "devDependencies": {
+    "@types/node": "^13.9.3",
+    "parcel-bundler": "^1.12.4",
+    "tailwindcss": "^1.2.0",
+    "typescript": "^3.8.3"
+  },
+  "dependencies": {
+    "@reduxjs/toolkit": "^1.2.5",
+    "@types/react-dom": "^16.9.5",
+    "@types/react-redux": "^7.1.7",
+    "@types/react-router-dom": "^5.1.3",
+    "contentful": "^7.14.0",
+    "react": "^16.13.1",
+    "react-dom": "^16.13.1",
+    "react-redux": "^7.2.0",
+    "react-router-dom": "^5.1.2"
+  }
+}
--- a/users/wpcarro/website/sandbox/contentful/postcss.config.js
+++ b/users/wpcarro/website/sandbox/contentful/postcss.config.js
@ -0,0 +1,5 @@
+const tailwindcss = require("tailwindcss");
+
+module.exports = {
+  plugins: [tailwindcss("./tailwind.config.js")],
+};
--- a/users/wpcarro/website/sandbox/contentful/shell.nix
+++ b/users/wpcarro/website/sandbox/contentful/shell.nix
@ -0,0 +1,9 @@
+let
+  briefcase = import <briefcase> {};
+  pkgs = briefcase.third_party.pkgs;
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    nodejs
+    yarn
+  ];
+}
--- a/users/wpcarro/website/sandbox/contentful/src/App.tsx
+++ b/users/wpcarro/website/sandbox/contentful/src/App.tsx
@ -0,0 +1,49 @@
+import React, { useEffect } from "react";
+import { BrowserRouter as Router, Switch, Route } from "react-router-dom";
+import { useDispatch } from "react-redux";
+import { actions, useTypedSelector } from "./store";
+import { Link } from "react-router-dom";
+import { getClient } from "./contentful";
+import type { Book } from "./store";
+
+const App: React.FC = () => {
+  const dispatch = useDispatch();
+  const { isLoading, books } = useTypedSelector((state) => ({
+    isLoading: state.isLoading,
+    books: state.books,
+  }));
+
+  useEffect(() => {
+    async function fetchData() {
+      const entries = await getClient().getEntries();
+      const books = entries.items.map((x) => x.fields) as Book[];
+
+      dispatch(actions.setBooks(books));
+    }
+    fetchData();
+  }, []);
+
+  return (
+    <Router>
+      <Switch>
+        <Route exact path="/">
+          <div className="container mx-auto">
+            <h1 className="py-6 text-2xl">Books</h1>
+            <ul>
+              {books.map((book) => (
+                <li key={book.title} className="py-3">
+                  <p>
+                    <span className="font-bold pr-3">{book.title}</span>
+                    <span className="text-gray-600">{book.author}</span>
+                  </p>
+                </li>
+              ))}
+            </ul>
+          </div>
+        </Route>
+      </Switch>
+    </Router>
+  );
+};
+
+export default App;
--- a/users/wpcarro/website/sandbox/contentful/src/contentful.ts
+++ b/users/wpcarro/website/sandbox/contentful/src/contentful.ts
@ -0,0 +1,27 @@
+import { createClient } from "contentful";
+import type { ContentfulClientApi } from "contentful";
+
+const space = process.env.CONTENTFUL_SPACE_ID;
+const accessToken = process.env.CONTENTFUL_ACCESS_TOKEN;
+
+let client: ContentfulClientApi;
+
+// Idempotent way to get a reference to the Contentful client.
+export const getClient = (): ContentfulClientApi => {
+  if (typeof client !== "undefined") {
+    return client;
+  } else {
+    if (typeof space === "string" && typeof accessToken === "string") {
+      let client = createClient({
+        space,
+        accessToken,
+      });
+
+      return client;
+    } else {
+      throw new Error(
+        "Please set CONTENTFUL_SPACE_ID and CONTENTFUL_ACCESS_TOKEN"
+      );
+    }
+  }
+};
--- a/users/wpcarro/website/sandbox/contentful/src/index.css
+++ b/users/wpcarro/website/sandbox/contentful/src/index.css
@ -0,0 +1,3 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
--- a/users/wpcarro/website/sandbox/contentful/src/index.html
+++ b/users/wpcarro/website/sandbox/contentful/src/index.html
@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="stylesheet" href="./index.css" />
+  </head>
+  <body>
+    <div id="mount"></div>
+    <script src="./index.tsx"></script>
+  </body>
+</html>
--- a/users/wpcarro/website/sandbox/contentful/src/index.tsx
+++ b/users/wpcarro/website/sandbox/contentful/src/index.tsx
@ -0,0 +1,12 @@
+import React from "react";
+import ReactDOM from "react-dom";
+import App from "./App";
+import { Provider } from "react-redux";
+import store from "./store";
+
+ReactDOM.render(
+  <Provider store={store}>
+    <App />
+  </Provider>,
+  document.getElementById("mount")
+);
--- a/users/wpcarro/website/sandbox/contentful/src/store.ts
+++ b/users/wpcarro/website/sandbox/contentful/src/store.ts
@ -0,0 +1,36 @@
+import { createSlice, configureStore, PayloadAction } from "@reduxjs/toolkit";
+import { useSelector, TypedUseSelectorHook } from "react-redux";
+
+export interface Book {
+  title: string;
+  author: string;
+  // TODO(wpcarro): Prefer datetime type here.
+  publicationDate: string;
+}
+
+export interface State {
+  isLoading: boolean;
+  books: Book[];
+}
+
+const initialState: State = {
+  isLoading: true,
+  books: [],
+};
+
+export const { actions, reducer } = createSlice({
+  name: "application",
+  initialState,
+  reducers: {
+    toggleIsLoading: (state) => ({ ...state, isLoading: !state.isLoading }),
+    setBooks: (state, action) => ({ ...state, books: action.payload }),
+  },
+});
+
+/**
+ * Defining and consuming this allows us to avoid annotating State in all of our
+ * selectors.
+ */
+export const useTypedSelector: TypedUseSelectorHook<State> = useSelector;
+
+export default configureStore({ reducer });
--- a/users/wpcarro/website/sandbox/contentful/tailwind.config.js
+++ b/users/wpcarro/website/sandbox/contentful/tailwind.config.js
@ -0,0 +1,7 @@
+module.exports = {
+  theme: {
+    extend: {},
+  },
+  variants: {},
+  plugins: [],
+};
--- a/users/wpcarro/website/sandbox/contentful/tsconfig.json
+++ b/users/wpcarro/website/sandbox/contentful/tsconfig.json
@ -0,0 +1,19 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "allowJs": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "allowSyntheticDefaultImports": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "module": "esnext",
+    "moduleResolution": "node",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true,
+    "jsx": "react"
+  },
+  "include": ["src/**/*"]
+}
--- a/users/wpcarro/website/sandbox/contentful/yarn.lock
+++ b/users/wpcarro/website/sandbox/contentful/yarn.lock
--- a/users/wpcarro/website/sandbox/covid-uk/default.nix.ignore
+++ b/users/wpcarro/website/sandbox/covid-uk/default.nix.ignore
@ -0,0 +1,16 @@
+{ pkgs, ... }:
+
+pkgs.stdenv.mkDerivation {
+  name = "covid-uk";
+  buildInputs = [];
+  src = builtins.path { path = ./.; name = "covid-uk"; };
+  # TODO(wpcarro): Need to run `yarn install` somehow.
+  # TODO(wpcarro): Need to run `npx tailwindcss build styles.css -o output.css`.
+  buildPhase = ''
+    mkdir -p $out
+    mkdir -p $out/node_modules/chart.js/dist
+    cp $src/node_modules/chart.js/dist/Chart.bundle.min.js $out/node_modules/chart.js/dist
+    cp $src/index.html $src/output.css $out
+  '';
+  dontInstall = true;
+}
--- a/users/wpcarro/website/sandbox/covid-uk/index.html
+++ b/users/wpcarro/website/sandbox/covid-uk/index.html
@ -0,0 +1,99 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>COVID-19 UK</title>
+  <link rel="stylesheet"  href="output.css">
+</head>
+<body class="container mx-auto py-10">
+  <div>
+    <h1 class="text-center">COVID-19 in the UK</h1>
+    <p>
+      Up until recently, I used a couple of resources (i.e.
+      <a href="https://multimedia.scmp.com/infographics/news/china/article/3047038/wuhan-virus/index.html">one</a>, 
+      <a href="https://www.worldometers.info/coronavirus/">two</a>) for tracking
+      an updated number of confirmed covid-19 cases.
+    </p>
+    <p>
+      Given the high speed at which the virus is spreading, I was having a
+      difficult time intuiting the shape of this growth. For example if today
+      the total number of confirmed cases for covid-19 in the UK was 500, I
+      could not remember if yesterday it was 450, 400, or 200.
+    </p>
+    <p>
+      Thankfully someone is <a
+      href="https://github.com/pomber/covid19">publishing this data</a> as a
+      timeseries database. I am currently living in London, so I decided to
+      chart the <u>daily number of confirmed covid-19 cases in the UK</u> to
+      better understand what is happening.
+    </p>
+  </div>
+  <canvas id="myChart" class="py-12"></canvas>
+  <script src="./node_modules/chart.js/dist/Chart.bundle.min.js"></script>
+  <script>
+   var timeseries =
+     fetch('https://pomber.github.io/covid19/timeseries.json')
+       .then(res => res.json())
+       .then(createChart);
+
+   function createChart(data) {
+     var uk = data["United Kingdom"];
+     var data = uk.map(x => x["confirmed"]);
+     var labels = uk.map(x => x["date"]);
+
+     var ctx = document.getElementById('myChart').getContext('2d');
+     var myChart = new Chart(ctx, {
+       type: 'line',
+       data: {
+         labels: labels,
+         datasets: [{
+           label: 'Number of confirmed COVID-19 cases in the U.K.',
+           data: data,
+           backgroundColor: 'rgba(255, 0, 100, 0.2)',
+           borderWidth: 3
+         }]
+       },
+       options: {
+         scales: {
+           yAxes: [{
+             ticks: {
+               beginAtZero: true
+             }
+           }]
+         }
+       }
+     });
+   }
+  </script>
+  <div>
+    <h2 class="text-center">Back of the envelope predictions</h2>
+    <p>
+      From what I have read, a population where 60% of its constituents have
+      been infected with covid-19 and have recovered is said to have "herd
+      immunity". Once a population has herd immunity, the rate at which the
+      virus spreads decreases.
+    </p>
+    <p>
+      Roughly 60M people live in the UK; 60% of 60M is around 40M. Before a
+      population reaches "herd immunity", the total number of <em>true
+      covid-19 cases</em> <u>doubles every five days</u>. Therefore in <u>fifty
+      days</u> you might expect the number of true cases to be <u>1000x
+      larger</u> than what it is today.
+    </p>
+    <p>
+      So if you think the total number of <em>true covid-19 cases</em>
+      <u>today</u> is 40,000 then you might expect the rate of growth to slow
+      down in a little less than two months.
+    </p>
+    <p>
+      Thank you for reading.
+    </p>
+  </div>
+  <footer class="pt-5 mb-8 lg:flex">
+    <a class="block py-2 lg:w-1/4 text-center hover:underline" href="https://learn.wpcarro.dev">Learn</a>
+    <a class="block py-2 lg:w-1/4 text-center hover:underline" href="https://blog.wpcarro.dev">Blog</a>
+    <a class="block py-2 lg:w-1/4 text-center hover:underline" href="https://twitter.com/wpcarro">Twitter</a>
+    <a class="block py-2 lg:w-1/4 text-center hover:underline" href="https://github.com/wpcarro">Github</a>
+  </footer>
+</body>
+</html>
--- a/users/wpcarro/website/sandbox/covid-uk/package.json
+++ b/users/wpcarro/website/sandbox/covid-uk/package.json
@ -0,0 +1,16 @@
+{
+  "name": "covid-uk",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "chart.js": "^2.9.3",
+    "tailwindcss": "^1.2.0"
+  }
+}
--- a/users/wpcarro/website/sandbox/covid-uk/shell.nix
+++ b/users/wpcarro/website/sandbox/covid-uk/shell.nix
@ -0,0 +1,9 @@
+let
+  briefcase = import <briefcase> {};
+  pkgs = briefcase.third_party.pkgs;
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    yarn
+    nodejs
+  ];
+}
--- a/users/wpcarro/website/sandbox/covid-uk/styles.css
+++ b/users/wpcarro/website/sandbox/covid-uk/styles.css
@ -0,0 +1,28 @@
+@tailwind base;
+
+body {
+  @apply font-mono;
+}
+
+h1 {
+  @apply text-3xl mb-5 font-bold;
+}
+
+h2 {
+  @apply text-2xl mb-5 font-bold;
+}
+
+h3 {
+  @apply text-xl mb-5 font-bold;
+}
+
+a {
+  @apply text-blue-600 underline;
+}
+
+p {
+  @apply mt-2 mb-5;
+}
+
+@tailwind components;
+@tailwind utilities;
--- a/users/wpcarro/website/sandbox/covid-uk/tailwind.config.js
+++ b/users/wpcarro/website/sandbox/covid-uk/tailwind.config.js
@ -0,0 +1,7 @@
+module.exports = {
+  theme: {
+    extend: {},
+  },
+  variants: {},
+  plugins: [],
+}
--- a/users/wpcarro/website/sandbox/covid-uk/yarn.lock
+++ b/users/wpcarro/website/sandbox/covid-uk/yarn.lock
@ -0,0 +1,542 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+"@types/color-name@^1.1.1":
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/@types/color-name/-/color-name-1.1.1.tgz#1c1261bbeaa10a8055bbc5d8ab84b7b2afc846a0"
+  integrity sha512-rr+OQyAjxze7GgWrSaJwydHStIhHq2lvY3BOC2Mj7KnzI7XK0Uw1TOOdI9lDoajEbSWLiYgoo4f1R51erQfhPQ==
+
+acorn-node@^1.6.1:
+  version "1.8.2"
+  resolved "https://registry.yarnpkg.com/acorn-node/-/acorn-node-1.8.2.tgz#114c95d64539e53dede23de8b9d96df7c7ae2af8"
+  integrity sha512-8mt+fslDufLYntIoPAaIMUe/lrbrehIiwmR3t2k9LljIzoigEPF27eLk2hy8zSGzmR/ogr7zbRKINMo1u0yh5A==
+  dependencies:
+    acorn "^7.0.0"
+    acorn-walk "^7.0.0"
+    xtend "^4.0.2"
+
+acorn-walk@^7.0.0:
+  version "7.1.1"
+  resolved "https://registry.yarnpkg.com/acorn-walk/-/acorn-walk-7.1.1.tgz#345f0dffad5c735e7373d2fec9a1023e6a44b83e"
+  integrity sha512-wdlPY2tm/9XBr7QkKlq0WQVgiuGTX6YWPyRyBviSoScBuLfTVQhvwg6wJ369GJ/1nPfTLMfnrFIfjqVg6d+jQQ==
+
+acorn@^7.0.0:
+  version "7.1.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.1.tgz#e35668de0b402f359de515c5482a1ab9f89a69bf"
+  integrity sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==
+
+ansi-styles@^3.2.1:
+  version "3.2.1"
+  resolved "https://registry.yarnpkg.com/ansi-styles/-/ansi-styles-3.2.1.tgz#41fbb20243e50b12be0f04b8dedbf07520ce841d"
+  integrity sha512-VT0ZI6kZRdTh8YyJw3SMbYm/u+NqfsAxEpWO0Pf9sq8/e94WxxOpPKx9FR1FlyCtOVDNOQ+8ntlqFxiRc+r5qA==
+  dependencies:
+    color-convert "^1.9.0"
+
+ansi-styles@^4.1.0:
+  version "4.2.1"
+  resolved "https://registry.yarnpkg.com/ansi-styles/-/ansi-styles-4.2.1.tgz#90ae75c424d008d2624c5bf29ead3177ebfcf359"
+  integrity sha512-9VGjrMsG1vePxcSweQsN20KY/c4zN0h9fLjqAbwbPfahM3t+NL+M9HC8xeXG2I8pX5NoamTGNuomEUFI7fcUjA==
+  dependencies:
+    "@types/color-name" "^1.1.1"
+    color-convert "^2.0.1"
+
+autoprefixer@^9.4.5:
+  version "9.7.4"
+  resolved "https://registry.yarnpkg.com/autoprefixer/-/autoprefixer-9.7.4.tgz#f8bf3e06707d047f0641d87aee8cfb174b2a5378"
+  integrity sha512-g0Ya30YrMBAEZk60lp+qfX5YQllG+S5W3GYCFvyHTvhOki0AEQJLPEcIuGRsqVwLi8FvXPVtwTGhfr38hVpm0g==
+  dependencies:
+    browserslist "^4.8.3"
+    caniuse-lite "^1.0.30001020"
+    chalk "^2.4.2"
+    normalize-range "^0.1.2"
+    num2fraction "^1.2.2"
+    postcss "^7.0.26"
+    postcss-value-parser "^4.0.2"
+
+balanced-match@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
+  integrity sha1-ibTRmasr7kneFk6gK4nORi1xt2c=
+
+brace-expansion@^1.1.7:
+  version "1.1.11"
+  resolved "https://registry.yarnpkg.com/brace-expansion/-/brace-expansion-1.1.11.tgz#3c7fcbf529d87226f3d2f52b966ff5271eb441dd"
+  integrity sha512-iCuPHDFgrHX7H2vEI/5xpz07zSHB00TpugqhmYtVmMO6518mCuRMoOYFldEBl0g187ufozdaHgWKcYFb61qGiA==
+  dependencies:
+    balanced-match "^1.0.0"
+    concat-map "0.0.1"
+
+browserslist@^4.8.3:
+  version "4.10.0"
+  resolved "https://registry.yarnpkg.com/browserslist/-/browserslist-4.10.0.tgz#f179737913eaf0d2b98e4926ac1ca6a15cbcc6a9"
+  integrity sha512-TpfK0TDgv71dzuTsEAlQiHeWQ/tiPqgNZVdv046fvNtBZrjbv2O3TsWCDU0AWGJJKCF/KsjNdLzR9hXOsh/CfA==
+  dependencies:
+    caniuse-lite "^1.0.30001035"
+    electron-to-chromium "^1.3.378"
+    node-releases "^1.1.52"
+    pkg-up "^3.1.0"
+
+bytes@^3.0.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/bytes/-/bytes-3.1.0.tgz#f6cf7933a360e0588fa9fde85651cdc7f805d1f6"
+  integrity sha512-zauLjrfCG+xvoyaqLoV8bLVXXNGC4JqlxFCutSDWA6fJrTo2ZuvLYTqZ7aHBLZSMOopbzwv8f+wZcVzfVTI2Dg==
+
+camelcase-css@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/camelcase-css/-/camelcase-css-2.0.1.tgz#ee978f6947914cc30c6b44741b6ed1df7f043fd5"
+  integrity sha512-QOSvevhslijgYwRx6Rv7zKdMF8lbRmx+uQGx2+vDc+KI/eBnsy9kit5aj23AgGu3pa4t9AgwbnXWqS+iOY+2aA==
+
+caniuse-lite@^1.0.30001020, caniuse-lite@^1.0.30001035:
+  version "1.0.30001035"
+  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001035.tgz#2bb53b8aa4716b2ed08e088d4dc816a5fe089a1e"
+  integrity sha512-C1ZxgkuA4/bUEdMbU5WrGY4+UhMFFiXrgNAfxiMIqWgFTWfv/xsZCS2xEHT2LMq7xAZfuAnu6mcqyDl0ZR6wLQ==
+
+chalk@^2.4.1, chalk@^2.4.2:
+  version "2.4.2"
+  resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.4.2.tgz#cd42541677a54333cf541a49108c1432b44c9424"
+  integrity sha512-Mti+f9lpJNcwF4tWV8/OrTTtF1gZi+f8FqlyAdouralcFWFQWF2+NgCHShjkCb+IFBLq9buZwE1xckQU4peSuQ==
+  dependencies:
+    ansi-styles "^3.2.1"
+    escape-string-regexp "^1.0.5"
+    supports-color "^5.3.0"
+
+chalk@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/chalk/-/chalk-3.0.0.tgz#3f73c2bf526591f574cc492c51e2456349f844e4"
+  integrity sha512-4D3B6Wf41KOYRFdszmDqMCGq5VV/uMAB273JILmO+3jAlh8X4qDtdtgCR3fxtbLEMzSx22QdhnDcJvu2u1fVwg==
+  dependencies:
+    ansi-styles "^4.1.0"
+    supports-color "^7.1.0"
+
+chart.js@^2.9.3:
+  version "2.9.3"
+  resolved "https://registry.yarnpkg.com/chart.js/-/chart.js-2.9.3.tgz#ae3884114dafd381bc600f5b35a189138aac1ef7"
+  integrity sha512-+2jlOobSk52c1VU6fzkh3UwqHMdSlgH1xFv9FKMqHiNCpXsGPQa/+81AFa+i3jZ253Mq9aAycPwDjnn1XbRNNw==
+  dependencies:
+    chartjs-color "^2.1.0"
+    moment "^2.10.2"
+
+chartjs-color-string@^0.6.0:
+  version "0.6.0"
+  resolved "https://registry.yarnpkg.com/chartjs-color-string/-/chartjs-color-string-0.6.0.tgz#1df096621c0e70720a64f4135ea171d051402f71"
+  integrity sha512-TIB5OKn1hPJvO7JcteW4WY/63v6KwEdt6udfnDE9iCAZgy+V4SrbSxoIbTw/xkUIapjEI4ExGtD0+6D3KyFd7A==
+  dependencies:
+    color-name "^1.0.0"
+
+chartjs-color@^2.1.0:
+  version "2.4.1"
+  resolved "https://registry.yarnpkg.com/chartjs-color/-/chartjs-color-2.4.1.tgz#6118bba202fe1ea79dd7f7c0f9da93467296c3b0"
+  integrity sha512-haqOg1+Yebys/Ts/9bLo/BqUcONQOdr/hoEr2LLTRl6C5LXctUdHxsCYfvQVg5JIxITrfCNUDr4ntqmQk9+/0w==
+  dependencies:
+    chartjs-color-string "^0.6.0"
+    color-convert "^1.9.3"
+
+color-convert@^1.9.0, color-convert@^1.9.3:
+  version "1.9.3"
+  resolved "https://registry.yarnpkg.com/color-convert/-/color-convert-1.9.3.tgz#bb71850690e1f136567de629d2d5471deda4c1e8"
+  integrity sha512-QfAUtd+vFdAtFQcC8CCyYt1fYWxSqAiK2cSD6zDB8N3cpsEBAvRxp9zOGg6G/SHHJYAT88/az/IuDGALsNVbGg==
+  dependencies:
+    color-name "1.1.3"
+
+color-convert@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/color-convert/-/color-convert-2.0.1.tgz#72d3a68d598c9bdb3af2ad1e84f21d896abd4de3"
+  integrity sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==
+  dependencies:
+    color-name "~1.1.4"
+
+color-name@1.1.3:
+  version "1.1.3"
+  resolved "https://registry.yarnpkg.com/color-name/-/color-name-1.1.3.tgz#a7d0558bd89c42f795dd42328f740831ca53bc25"
+  integrity sha1-p9BVi9icQveV3UIyj3QIMcpTvCU=
+
+color-name@^1.0.0, color-name@~1.1.4:
+  version "1.1.4"
+  resolved "https://registry.yarnpkg.com/color-name/-/color-name-1.1.4.tgz#c2a09a87acbde69543de6f63fa3995c826c536a2"
+  integrity sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==
+
+concat-map@0.0.1:
+  version "0.0.1"
+  resolved "https://registry.yarnpkg.com/concat-map/-/concat-map-0.0.1.tgz#d8a96bd77fd68df7793a73036a3ba0d5405d477b"
+  integrity sha1-2Klr13/Wjfd5OnMDajug1UBdR3s=
+
+css-unit-converter@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/css-unit-converter/-/css-unit-converter-1.1.1.tgz#d9b9281adcfd8ced935bdbaba83786897f64e996"
+  integrity sha1-2bkoGtz9jO2TW9urqDeGiX9k6ZY=
+
+cssesc@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/cssesc/-/cssesc-3.0.0.tgz#37741919903b868565e1c09ea747445cd18983ee"
+  integrity sha512-/Tb/JcjK111nNScGob5MNtsntNM1aCNUDipB/TkwZFhyDrrE47SOx/18wF2bbjgc3ZzCSKW1T5nt5EbFoAz/Vg==
+
+defined@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/defined/-/defined-1.0.0.tgz#c98d9bcef75674188e110969151199e39b1fa693"
+  integrity sha1-yY2bzvdWdBiOEQlpFRGZ45sfppM=
+
+detective@^5.2.0:
+  version "5.2.0"
+  resolved "https://registry.yarnpkg.com/detective/-/detective-5.2.0.tgz#feb2a77e85b904ecdea459ad897cc90a99bd2a7b"
+  integrity sha512-6SsIx+nUUbuK0EthKjv0zrdnajCCXVYGmbYYiYjFVpzcjwEs/JMDZ8tPRG29J/HhN56t3GJp2cGSWDRjjot8Pg==
+  dependencies:
+    acorn-node "^1.6.1"
+    defined "^1.0.0"
+    minimist "^1.1.1"
+
+electron-to-chromium@^1.3.378:
+  version "1.3.379"
+  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.379.tgz#81dc5e82a3e72bbb830d93e15bc35eda2bbc910e"
+  integrity sha512-NK9DBBYEBb5f9D7zXI0hiE941gq3wkBeQmXs1ingigA/jnTg5mhwY2Z5egwA+ZI8OLGKCx0h1Cl8/xeuIBuLlg==
+
+escape-string-regexp@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz#1b61c0562190a8dff6ae3bb2cf0200ca130b86d4"
+  integrity sha1-G2HAViGQqN/2rjuyzwIAyhMLhtQ=
+
+find-up@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/find-up/-/find-up-3.0.0.tgz#49169f1d7993430646da61ecc5ae355c21c97b73"
+  integrity sha512-1yD6RmLI1XBfxugvORwlck6f75tYL+iR0jqwsOrOxMZyGYqUuDhJ0l4AXdO1iX/FTs9cBAMEk1gWSEx1kSbylg==
+  dependencies:
+    locate-path "^3.0.0"
+
+fs-extra@^8.0.0:
+  version "8.1.0"
+  resolved "https://registry.yarnpkg.com/fs-extra/-/fs-extra-8.1.0.tgz#49d43c45a88cd9677668cb7be1b46efdb8d2e1c0"
+  integrity sha512-yhlQgA6mnOJUKOsRUFsgJdQCvkKhcz8tlZG5HBQfReYZy46OwLcY+Zia0mtdHsOo9y/hP+CxMN0TU9QxoOtG4g==
+  dependencies:
+    graceful-fs "^4.2.0"
+    jsonfile "^4.0.0"
+    universalify "^0.1.0"
+
+fs.realpath@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/fs.realpath/-/fs.realpath-1.0.0.tgz#1504ad2523158caa40db4a2787cb01411994ea4f"
+  integrity sha1-FQStJSMVjKpA20onh8sBQRmU6k8=
+
+glob@^7.1.2:
+  version "7.1.6"
+  resolved "https://registry.yarnpkg.com/glob/-/glob-7.1.6.tgz#141f33b81a7c2492e125594307480c46679278a6"
+  integrity sha512-LwaxwyZ72Lk7vZINtNNrywX0ZuLyStrdDtabefZKAY5ZGJhVtgdznluResxNmPitE0SAO+O26sWTHeKSI2wMBA==
+  dependencies:
+    fs.realpath "^1.0.0"
+    inflight "^1.0.4"
+    inherits "2"
+    minimatch "^3.0.4"
+    once "^1.3.0"
+    path-is-absolute "^1.0.0"
+
+graceful-fs@^4.1.6, graceful-fs@^4.2.0:
+  version "4.2.3"
+  resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.2.3.tgz#4a12ff1b60376ef09862c2093edd908328be8423"
+  integrity sha512-a30VEBm4PEdx1dRB7MFK7BejejvCvBronbLjht+sHuGYj8PHs7M/5Z+rt5lw551vZ7yfTCj4Vuyy3mSJytDWRQ==
+
+has-flag@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/has-flag/-/has-flag-3.0.0.tgz#b5d454dc2199ae225699f3467e5a07f3b955bafd"
+  integrity sha1-tdRU3CGZriJWmfNGfloH87lVuv0=
+
+has-flag@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/has-flag/-/has-flag-4.0.0.tgz#944771fd9c81c81265c4d6941860da06bb59479b"
+  integrity sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==
+
+indexes-of@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/indexes-of/-/indexes-of-1.0.1.tgz#f30f716c8e2bd346c7b67d3df3915566a7c05607"
+  integrity sha1-8w9xbI4r00bHtn0985FVZqfAVgc=
+
+inflight@^1.0.4:
+  version "1.0.6"
+  resolved "https://registry.yarnpkg.com/inflight/-/inflight-1.0.6.tgz#49bd6331d7d02d0c09bc910a1075ba8165b56df9"
+  integrity sha1-Sb1jMdfQLQwJvJEKEHW6gWW1bfk=
+  dependencies:
+    once "^1.3.0"
+    wrappy "1"
+
+inherits@2:
+  version "2.0.4"
+  resolved "https://registry.yarnpkg.com/inherits/-/inherits-2.0.4.tgz#0fa2c64f932917c3433a0ded55363aae37416b7c"
+  integrity sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==
+
+jsonfile@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/jsonfile/-/jsonfile-4.0.0.tgz#8771aae0799b64076b76640fca058f9c10e33ecb"
+  integrity sha1-h3Gq4HmbZAdrdmQPygWPnBDjPss=
+  optionalDependencies:
+    graceful-fs "^4.1.6"
+
+locate-path@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/locate-path/-/locate-path-3.0.0.tgz#dbec3b3ab759758071b58fe59fc41871af21400e"
+  integrity sha512-7AO748wWnIhNqAuaty2ZWHkQHRSNfPVIsPIfwEOWO22AmaoVrWavlOcMR5nzTLNYvp36X220/maaRsrec1G65A==
+  dependencies:
+    p-locate "^3.0.0"
+    path-exists "^3.0.0"
+
+lodash.toarray@^4.4.0:
+  version "4.4.0"
+  resolved "https://registry.yarnpkg.com/lodash.toarray/-/lodash.toarray-4.4.0.tgz#24c4bfcd6b2fba38bfd0594db1179d8e9b656561"
+  integrity sha1-JMS/zWsvuji/0FlNsRedjptlZWE=
+
+lodash@^4.17.15:
+  version "4.17.15"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
+  integrity sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A==
+
+minimatch@^3.0.4:
+  version "3.0.4"
+  resolved "https://registry.yarnpkg.com/minimatch/-/minimatch-3.0.4.tgz#5166e286457f03306064be5497e8dbb0c3d32083"
+  integrity sha512-yJHVQEhyqPLUTgt9B83PXu6W3rx4MvvHvSUvToogpwoGDOUQ+yDrR0HRot+yOCdCO7u4hX3pWft6kWBBcqh0UA==
+  dependencies:
+    brace-expansion "^1.1.7"
+
+minimist@^1.1.1:
+  version "1.2.5"
+  resolved "https://registry.yarnpkg.com/minimist/-/minimist-1.2.5.tgz#67d66014b66a6a8aaa0c083c5fd58df4e4e97602"
+  integrity sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==
+
+moment@^2.10.2:
+  version "2.24.0"
+  resolved "https://registry.yarnpkg.com/moment/-/moment-2.24.0.tgz#0d055d53f5052aa653c9f6eb68bb5d12bf5c2b5b"
+  integrity sha512-bV7f+6l2QigeBBZSM/6yTNq4P2fNpSWj/0e7jQcy87A8e7o2nAfP/34/2ky5Vw4B9S446EtIhodAzkFCcR4dQg==
+
+node-emoji@^1.8.1:
+  version "1.10.0"
+  resolved "https://registry.yarnpkg.com/node-emoji/-/node-emoji-1.10.0.tgz#8886abd25d9c7bb61802a658523d1f8d2a89b2da"
+  integrity sha512-Yt3384If5H6BYGVHiHwTL+99OzJKHhgp82S8/dktEK73T26BazdgZ4JZh92xSVtGNJvz9UbXdNAc5hcrXV42vw==
+  dependencies:
+    lodash.toarray "^4.4.0"
+
+node-releases@^1.1.52:
+  version "1.1.52"
+  resolved "https://registry.yarnpkg.com/node-releases/-/node-releases-1.1.52.tgz#bcffee3e0a758e92e44ecfaecd0a47554b0bcba9"
+  integrity sha512-snSiT1UypkgGt2wxPqS6ImEUICbNCMb31yaxWrOLXjhlt2z2/IBpaOxzONExqSm4y5oLnAqjjRWu+wsDzK5yNQ==
+  dependencies:
+    semver "^6.3.0"
+
+normalize-range@^0.1.2:
+  version "0.1.2"
+  resolved "https://registry.yarnpkg.com/normalize-range/-/normalize-range-0.1.2.tgz#2d10c06bdfd312ea9777695a4d28439456b75942"
+  integrity sha1-LRDAa9/TEuqXd2laTShDlFa3WUI=
+
+normalize.css@^8.0.1:
+  version "8.0.1"
+  resolved "https://registry.yarnpkg.com/normalize.css/-/normalize.css-8.0.1.tgz#9b98a208738b9cc2634caacbc42d131c97487bf3"
+  integrity sha512-qizSNPO93t1YUuUhP22btGOo3chcvDFqFaj2TRybP0DMxkHOCTYwp3n34fel4a31ORXy4m1Xq0Gyqpb5m33qIg==
+
+num2fraction@^1.2.2:
+  version "1.2.2"
+  resolved "https://registry.yarnpkg.com/num2fraction/-/num2fraction-1.2.2.tgz#6f682b6a027a4e9ddfa4564cd2589d1d4e669ede"
+  integrity sha1-b2gragJ6Tp3fpFZM0lidHU5mnt4=
+
+object-assign@^4.1.1:
+  version "4.1.1"
+  resolved "https://registry.yarnpkg.com/object-assign/-/object-assign-4.1.1.tgz#2109adc7965887cfc05cbbd442cac8bfbb360863"
+  integrity sha1-IQmtx5ZYh8/AXLvUQsrIv7s2CGM=
+
+once@^1.3.0:
+  version "1.4.0"
+  resolved "https://registry.yarnpkg.com/once/-/once-1.4.0.tgz#583b1aa775961d4b113ac17d9c50baef9dd76bd1"
+  integrity sha1-WDsap3WWHUsROsF9nFC6753Xa9E=
+  dependencies:
+    wrappy "1"
+
+p-limit@^2.0.0:
+  version "2.2.2"
+  resolved "https://registry.yarnpkg.com/p-limit/-/p-limit-2.2.2.tgz#61279b67721f5287aa1c13a9a7fbbc48c9291b1e"
+  integrity sha512-WGR+xHecKTr7EbUEhyLSh5Dube9JtdiG78ufaeLxTgpudf/20KqyMioIUZJAezlTIi6evxuoUs9YXc11cU+yzQ==
+  dependencies:
+    p-try "^2.0.0"
+
+p-locate@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/p-locate/-/p-locate-3.0.0.tgz#322d69a05c0264b25997d9f40cd8a891ab0064a4"
+  integrity sha512-x+12w/To+4GFfgJhBEpiDcLozRJGegY+Ei7/z0tSLkMmxGZNybVMSfWj9aJn8Z5Fc7dBUNJOOVgPv2H7IwulSQ==
+  dependencies:
+    p-limit "^2.0.0"
+
+p-try@^2.0.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/p-try/-/p-try-2.2.0.tgz#cb2868540e313d61de58fafbe35ce9004d5540e6"
+  integrity sha512-R4nPAVTAU0B9D35/Gk3uJf/7XYbQcyohSKdvAxIRSNghFl4e71hVoGnBNQz9cWaXxO2I10KTC+3jMdvvoKw6dQ==
+
+path-exists@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/path-exists/-/path-exists-3.0.0.tgz#ce0ebeaa5f78cb18925ea7d810d7b59b010fd515"
+  integrity sha1-zg6+ql94yxiSXqfYENe1mwEP1RU=
+
+path-is-absolute@^1.0.0:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/path-is-absolute/-/path-is-absolute-1.0.1.tgz#174b9268735534ffbc7ace6bf53a5a9e1b5c5f5f"
+  integrity sha1-F0uSaHNVNP+8es5r9TpanhtcX18=
+
+path-parse@^1.0.6:
+  version "1.0.6"
+  resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.6.tgz#d62dbb5679405d72c4737ec58600e9ddcf06d24c"
+  integrity sha512-GSmOT2EbHrINBf9SR7CDELwlJ8AENk3Qn7OikK4nFYAu3Ote2+JYNVvkpAEQm3/TLNEJFD/xZJjzyxg3KBWOzw==
+
+pkg-up@^3.1.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/pkg-up/-/pkg-up-3.1.0.tgz#100ec235cc150e4fd42519412596a28512a0def5"
+  integrity sha512-nDywThFk1i4BQK4twPQ6TA4RT8bDY96yeuCVBWL3ePARCiEKDRSrNGbFIgUJpLp+XeIR65v8ra7WuJOFUBtkMA==
+  dependencies:
+    find-up "^3.0.0"
+
+postcss-functions@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/postcss-functions/-/postcss-functions-3.0.0.tgz#0e94d01444700a481de20de4d55fb2640564250e"
+  integrity sha1-DpTQFERwCkgd4g3k1V+yZAVkJQ4=
+  dependencies:
+    glob "^7.1.2"
+    object-assign "^4.1.1"
+    postcss "^6.0.9"
+    postcss-value-parser "^3.3.0"
+
+postcss-js@^2.0.0:
+  version "2.0.3"
+  resolved "https://registry.yarnpkg.com/postcss-js/-/postcss-js-2.0.3.tgz#a96f0f23ff3d08cec7dc5b11bf11c5f8077cdab9"
+  integrity sha512-zS59pAk3deu6dVHyrGqmC3oDXBdNdajk4k1RyxeVXCrcEDBUBHoIhE4QTsmhxgzXxsaqFDAkUZfmMa5f/N/79w==
+  dependencies:
+    camelcase-css "^2.0.1"
+    postcss "^7.0.18"
+
+postcss-nested@^4.1.1:
+  version "4.2.1"
+  resolved "https://registry.yarnpkg.com/postcss-nested/-/postcss-nested-4.2.1.tgz#4bc2e5b35e3b1e481ff81e23b700da7f82a8b248"
+  integrity sha512-AMayXX8tS0HCp4O4lolp4ygj9wBn32DJWXvG6gCv+ZvJrEa00GUxJcJEEzMh87BIe6FrWdYkpR2cuyqHKrxmXw==
+  dependencies:
+    postcss "^7.0.21"
+    postcss-selector-parser "^6.0.2"
+
+postcss-selector-parser@^6.0.0, postcss-selector-parser@^6.0.2:
+  version "6.0.2"
+  resolved "https://registry.yarnpkg.com/postcss-selector-parser/-/postcss-selector-parser-6.0.2.tgz#934cf799d016c83411859e09dcecade01286ec5c"
+  integrity sha512-36P2QR59jDTOAiIkqEprfJDsoNrvwFei3eCqKd1Y0tUsBimsq39BLp7RD+JWny3WgB1zGhJX8XVePwm9k4wdBg==
+  dependencies:
+    cssesc "^3.0.0"
+    indexes-of "^1.0.1"
+    uniq "^1.0.1"
+
+postcss-value-parser@^3.3.0:
+  version "3.3.1"
+  resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-3.3.1.tgz#9ff822547e2893213cf1c30efa51ac5fd1ba8281"
+  integrity sha512-pISE66AbVkp4fDQ7VHBwRNXzAAKJjw4Vw7nWI/+Q3vuly7SNfgYXvm6i5IgFylHGK5sP/xHAbB7N49OS4gWNyQ==
+
+postcss-value-parser@^4.0.2:
+  version "4.0.3"
+  resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-4.0.3.tgz#651ff4593aa9eda8d5d0d66593a2417aeaeb325d"
+  integrity sha512-N7h4pG+Nnu5BEIzyeaaIYWs0LI5XC40OrRh5L60z0QjFsqGWcHcbkBvpe1WYpcIS9yQ8sOi/vIPt1ejQCrMVrg==
+
+postcss@^6.0.9:
+  version "6.0.23"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-6.0.23.tgz#61c82cc328ac60e677645f979054eb98bc0e3324"
+  integrity sha512-soOk1h6J3VMTZtVeVpv15/Hpdl2cBLX3CAw4TAbkpTJiNPk9YP/zWcD1ND+xEtvyuuvKzbxliTOIyvkSeSJ6ag==
+  dependencies:
+    chalk "^2.4.1"
+    source-map "^0.6.1"
+    supports-color "^5.4.0"
+
+postcss@^7.0.11, postcss@^7.0.18, postcss@^7.0.21, postcss@^7.0.26:
+  version "7.0.27"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-7.0.27.tgz#cc67cdc6b0daa375105b7c424a85567345fc54d9"
+  integrity sha512-WuQETPMcW9Uf1/22HWUWP9lgsIC+KEHg2kozMflKjbeUtw9ujvFX6QmIfozaErDkmLWS9WEnEdEe6Uo9/BNTdQ==
+  dependencies:
+    chalk "^2.4.2"
+    source-map "^0.6.1"
+    supports-color "^6.1.0"
+
+pretty-hrtime@^1.0.3:
+  version "1.0.3"
+  resolved "https://registry.yarnpkg.com/pretty-hrtime/-/pretty-hrtime-1.0.3.tgz#b7e3ea42435a4c9b2759d99e0f201eb195802ee1"
+  integrity sha1-t+PqQkNaTJsnWdmeDyAesZWALuE=
+
+reduce-css-calc@^2.1.6:
+  version "2.1.7"
+  resolved "https://registry.yarnpkg.com/reduce-css-calc/-/reduce-css-calc-2.1.7.tgz#1ace2e02c286d78abcd01fd92bfe8097ab0602c2"
+  integrity sha512-fDnlZ+AybAS3C7Q9xDq5y8A2z+lT63zLbynew/lur/IR24OQF5x98tfNwf79mzEdfywZ0a2wpM860FhFfMxZlA==
+  dependencies:
+    css-unit-converter "^1.1.1"
+    postcss-value-parser "^3.3.0"
+
+resolve@^1.14.2:
+  version "1.15.1"
+  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.15.1.tgz#27bdcdeffeaf2d6244b95bb0f9f4b4653451f3e8"
+  integrity sha512-84oo6ZTtoTUpjgNEr5SJyzQhzL72gaRodsSfyxC/AXRvwu0Yse9H8eF9IpGo7b8YetZhlI6v7ZQ6bKBFV/6S7w==
+  dependencies:
+    path-parse "^1.0.6"
+
+semver@^6.3.0:
+  version "6.3.0"
+  resolved "https://registry.yarnpkg.com/semver/-/semver-6.3.0.tgz#ee0a64c8af5e8ceea67687b133761e1becbd1d3d"
+  integrity sha512-b39TBaTSfV6yBrapU89p5fKekE2m/NwnDocOVruQFS1/veMgdzuPcnOM34M6CwxW8jH/lxEa5rBoDeUwu5HHTw==
+
+source-map@^0.6.1:
+  version "0.6.1"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
+  integrity sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==
+
+supports-color@^5.3.0, supports-color@^5.4.0:
+  version "5.5.0"
+  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-5.5.0.tgz#e2e69a44ac8772f78a1ec0b35b689df6530efc8f"
+  integrity sha512-QjVjwdXIt408MIiAqCX4oUKsgU2EqAGzs2Ppkm4aQYbjm+ZEWEcW4SfFNTr4uMNZma0ey4f5lgLrkB0aX0QMow==
+  dependencies:
+    has-flag "^3.0.0"
+
+supports-color@^6.1.0:
+  version "6.1.0"
+  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-6.1.0.tgz#0764abc69c63d5ac842dd4867e8d025e880df8f3"
+  integrity sha512-qe1jfm1Mg7Nq/NSh6XE24gPXROEVsWHxC1LIx//XNlD9iw7YZQGjZNjYN7xGaEG6iKdA8EtNFW6R0gjnVXp+wQ==
+  dependencies:
+    has-flag "^3.0.0"
+
+supports-color@^7.1.0:
+  version "7.1.0"
+  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-7.1.0.tgz#68e32591df73e25ad1c4b49108a2ec507962bfd1"
+  integrity sha512-oRSIpR8pxT1Wr2FquTNnGet79b3BWljqOuoW/h4oBhxJ/HUbX5nX6JSruTkvXDCFMwDPvsaTTbvMLKZWSy0R5g==
+  dependencies:
+    has-flag "^4.0.0"
+
+tailwindcss@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/tailwindcss/-/tailwindcss-1.2.0.tgz#5df317cebac4f3131f275d258a39da1ba3a0f291"
+  integrity sha512-CKvY0ytB3ze5qvynG7qv4XSpQtFNGPbu9pUn8qFdkqgD8Yo/vGss8mhzbqls44YCXTl4G62p3qVZBj45qrd6FQ==
+  dependencies:
+    autoprefixer "^9.4.5"
+    bytes "^3.0.0"
+    chalk "^3.0.0"
+    detective "^5.2.0"
+    fs-extra "^8.0.0"
+    lodash "^4.17.15"
+    node-emoji "^1.8.1"
+    normalize.css "^8.0.1"
+    postcss "^7.0.11"
+    postcss-functions "^3.0.0"
+    postcss-js "^2.0.0"
+    postcss-nested "^4.1.1"
+    postcss-selector-parser "^6.0.0"
+    pretty-hrtime "^1.0.3"
+    reduce-css-calc "^2.1.6"
+    resolve "^1.14.2"
+
+uniq@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/uniq/-/uniq-1.0.1.tgz#b31c5ae8254844a3a8281541ce2b04b865a734ff"
+  integrity sha1-sxxa6CVIRKOoKBVBzisEuGWnNP8=
+
+universalify@^0.1.0:
+  version "0.1.2"
+  resolved "https://registry.yarnpkg.com/universalify/-/universalify-0.1.2.tgz#b646f69be3942dabcecc9d6639c80dc105efaa66"
+  integrity sha512-rBJeI5CXAlmy1pV+617WB9J63U6XcazHHF2f2dbJix4XzpUF0RS3Zbj0FGIOCAva5P/d/GBOYaACQ1w+0azUkg==
+
+wrappy@1:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/wrappy/-/wrappy-1.0.2.tgz#b5243d8f3ec1aa35f1364605bc0d1036e30ab69f"
+  integrity sha1-tSQ9jz7BqjXxNkYFvA0QNuMKtp8=
+
+xtend@^4.0.2:
+  version "4.0.2"
+  resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.2.tgz#bb72779f5fa465186b1f438f674fa347fdb5db54"
+  integrity sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==
--- a/users/wpcarro/website/sandbox/default.nix.ignore
+++ b/users/wpcarro/website/sandbox/default.nix.ignore
@ -0,0 +1,13 @@
+{ pkgs, briefcase, ... }:
+
+pkgs.stdenv.mkDerivation {
+  name = "covid-uk";
+  buildInputs = [];
+  src = builtins.path { path = ./.; name = "sandbox"; };
+  buildPhase = ''
+    mkdir -p $out
+    cp $src/index.html $out
+    cp -r ${briefcase.website.sandbox.covid-uk} $out/covid-uk
+  '';
+  dontInstall = true;
+}
--- a/users/wpcarro/website/sandbox/github-issues-service/README.md
+++ b/users/wpcarro/website/sandbox/github-issues-service/README.md
@ -0,0 +1,28 @@
+# Github Issues Service (GIS)
+
+> 'Cause I got issues. But you got 'em too...
+> - [Issues by Julia Michaels][issues]
+
+You have a website and your users want to request features or report bugs. How
+do they do this?
+
+Our robot, GIS, can help you. GIS adds a widget to your website that allows
+users to easily request features and report bugs.
+
+## Getting Started
+
+If Github is hosting your website's source code, you're ready to start using
+GIS. GIS works with public and private repositories.
+
+Let's adopt Github's notion of "issues" to group feature requests and bug
+reports together. When users click the GIS widget to create an issue, GIS
+displays a modal form that the user completes. When the user submits the form,
+GIS creates an issue on your Github repository. Now your team can use all of
+Github's rich issue-tracking tools to manage your issues.
+
+## Installation
+
+To add GIS to your website, register your Github repository with us and we'll
+give you a snippet to add to your website's HTML. It's that simple.
+
+[issues]: https://www.youtube.com/watch?v=9Ke4480MicU
--- a/users/wpcarro/website/sandbox/index.html
+++ b/users/wpcarro/website/sandbox/index.html
@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>sandbox.wpcarro.dev</title>
+  </head>
+  <body>
+    <h1>Projects</h1>
+    <ul>
+      <li>
+        <a href="/covid-uk">COVID-19 in the UK</a>
+      </li>
+    </ul>
+  </body>
+</html>
--- a/users/wpcarro/website/sandbox/learnpianochords/.envrc
+++ b/users/wpcarro/website/sandbox/learnpianochords/.envrc
@ -0,0 +1,2 @@
+source_up
+use_nix
--- a/users/wpcarro/website/sandbox/learnpianochords/.gitignore
+++ b/users/wpcarro/website/sandbox/learnpianochords/.gitignore
@ -0,0 +1,3 @@
+/elm-stuff
+/Main.min.js
+/output.css
--- a/users/wpcarro/website/sandbox/learnpianochords/README.md
+++ b/users/wpcarro/website/sandbox/learnpianochords/README.md
@ -0,0 +1,57 @@
+# Learn Piano Chords (LPC)
+
+Are you a musician looking for a more effective way to improve your craft? Maybe
+you're a music teacher looking to create useful exercises to give your students.
+
+Studying music theory can be a fruitful undertaking, but it can often overwhelm
+or bore students. I think that if practicing is enjoyable, students will
+practice more. Practice doesn't make perfect; *perfect* practice makes perfect.
+Learn Piano Chords is a web app that lowers the barrier to practicing and
+internalizing music theory.
+
+## How does it work?
+
+1. Grab a cell phone or a laptop and your instrument.
+2. Open a web browser and visit the Learn Piano Chords app (URL and app
+   forthcoming).
+6. Set the tempo (i.e. pace) at which you would like to practice.
+4. Set the target duration of your session.
+5. Select the key(s) and chord(s) you would like to practice.
+7. LPC will display chords at various rhythmic intervals during your practice
+   session. It is your job to play these chords in time before the next chord
+   appears.
+
+## Highlights
+
+Here are some useful features of LPC:
+- Tempo: Set the rate at which LPC displays chords.
+- Predefined practice sessions: LPC offers users a few practice sessions to get
+  users started. The goal, however, is to teach users to create their own
+  bespoke practice sessions. LPC aims to foster a community of practitioners who
+  curate and share their practice sessions.
+- Whitelist / blacklist: Construct the set of chords you would like to
+  practice. Let's say you only want to practice triads in the keys of F, C, and
+  G. Would you also like to avoid diminished chords? Or maybe you *only* want to
+  practice major-7th chords for *all* keys. LPC supports all of these scenarios
+  and many others. You can save these chord configurations to reuse them at any
+  time. You can also share chord configurations with other LPC users if you find
+  the practice useful.
+- Inversions: Every chord has inversions. For instance, every triad (i.e. chord
+  composed of three notes) has three inversions: root, second, and third
+  positions. LPC acknowledges all of the positions in which chords may appear
+  and helps you study all, some, or none of these inversions.
+- Harmony: LPC understands basic harmony and can sort the chords you would like
+  to train in various harmonious permutations.
+- Chaos-mode: Feeling confident? Throw the classical notions of harmony to the
+  wayside and use LPC in "chaos-mode" where LPC samples randomly from the Circle
+  of Fifths.
+
+## Developing
+
+If you're interested in contributing, the following will create an environment
+in which you can develop:
+
+```shell
+$ nix-shell
+$ elm-live -- src/Main.elm --output=elm.js
+```
--- a/users/wpcarro/website/sandbox/learnpianochords/default.nix
+++ b/users/wpcarro/website/sandbox/learnpianochords/default.nix
@ -0,0 +1,60 @@
+{ pkgs ? <nixpkgs>, ... }:
+
+with pkgs;
+
+let
+  mkDerivation =
+    { srcs ? ./elm-srcs.nix
+    , src
+    , name
+    , srcdir ? "./src"
+    , targets ? []
+    , registryDat ? ./registry.dat
+    , outputJavaScript ? false
+    }:
+    stdenv.mkDerivation {
+      inherit name src;
+
+      buildInputs = [ elmPackages.elm ]
+        ++ lib.optional outputJavaScript nodePackages_10_x.uglify-js;
+
+      buildPhase = pkgs.elmPackages.fetchElmDeps {
+        elmPackages = import srcs;
+        elmVersion = "0.19.1";
+        inherit registryDat;
+      };
+
+      installPhase = let
+        elmfile = module: "${srcdir}/${builtins.replaceStrings ["."] ["/"] module}.elm";
+        extension = if outputJavaScript then "js" else "html";
+      in ''
+        mkdir -p $out/share/doc
+        ${lib.concatStrings (map (module: ''
+          echo "compiling ${elmfile module}"
+          elm make ${elmfile module} --output $out/${module}.${extension} --docs $out/share/doc/${module}.json
+          ${lib.optionalString outputJavaScript ''
+            echo "minifying ${elmfile module}"
+            uglifyjs $out/${module}.${extension} --compress 'pure_funcs="F2,F3,F4,F5,F6,F7,F8,F9,A2,A3,A4,A5,A6,A7,A8,A9",pure_getters,keep_fargs=false,unsafe_comps,unsafe' \
+                | uglifyjs --mangle --output=$out/${module}.min.${extension}
+          ''}
+        '') targets)}
+      '';
+    };
+  mainDotElm = mkDerivation {
+    name = "elm-app-0.1.0";
+    srcs = ./elm-srcs.nix;
+    src = builtins.path { path = ./.; name = "learnpianochords"; };
+    targets = ["Main"];
+    srcdir = "./src";
+    outputJavaScript = true;
+  };
+in stdenv.mkDerivation {
+  name = "learn-piano-chords";
+  buildInputs = [];
+  src = builtins.path { path = ./.; name = "learnpianochords"; };
+  buildPhase = ''
+    mkdir -p $out
+    cp index.html output.css ${mainDotElm}/Main.min.js $out
+  '';
+  dontInstall = true;
+}
--- a/users/wpcarro/website/sandbox/learnpianochords/elm-srcs.nix
+++ b/users/wpcarro/website/sandbox/learnpianochords/elm-srcs.nix
@ -0,0 +1,67 @@
+{
+
+      "elm-community/maybe-extra" = {
+        sha256 = "0qslmgswa625d218djd3p62pnqcrz38f5p558mbjl6kc1ss0kzv3";
+        version = "5.2.0";
+      };
+
+      "elm/html" = {
+        sha256 = "1n3gpzmpqqdsldys4ipgyl1zacn0kbpc3g4v3hdpiyfjlgh8bf3k";
+        version = "1.0.0";
+      };
+
+      "elm-community/random-extra" = {
+        sha256 = "1dg2nz77w2cvp16xazbdsxkkw0xc9ycqpkd032faqdyky6gmz9g6";
+        version = "3.1.0";
+      };
+
+      "elm/svg" = {
+        sha256 = "1cwcj73p61q45wqwgqvrvz3aypjyy3fw732xyxdyj6s256hwkn0k";
+        version = "1.0.1";
+      };
+
+      "elm/browser" = {
+        sha256 = "0nagb9ajacxbbg985r4k9h0jadqpp0gp84nm94kcgbr5sf8i9x13";
+        version = "1.0.2";
+      };
+
+      "elm/core" = {
+        sha256 = "19w0iisdd66ywjayyga4kv2p1v9rxzqjaxhckp8ni6n8i0fb2dvf";
+        version = "1.0.5";
+      };
+
+      "elm-community/list-extra" = {
+        sha256 = "1ayv3148drynqnxdfwpjxal8vwzgsjqanjg7yxp6lhdcbkxgd3vd";
+        version = "8.2.3";
+      };
+
+      "elm/random" = {
+        sha256 = "138n2455wdjwa657w6sjq18wx2r0k60ibpc4frhbqr50sncxrfdl";
+        version = "1.0.0";
+      };
+
+      "elm/time" = {
+        sha256 = "0vch7i86vn0x8b850w1p69vplll1bnbkp8s383z7pinyg94cm2z1";
+        version = "1.0.0";
+      };
+
+      "elm/json" = {
+        sha256 = "0kjwrz195z84kwywaxhhlnpl3p251qlbm5iz6byd6jky2crmyqyh";
+        version = "1.1.3";
+      };
+
+      "owanturist/elm-union-find" = {
+        sha256 = "13gm7msnp0gr1lqia5m7m4lhy3m6kvjg37d304whb3psn88wqhj5";
+        version = "1.0.0";
+      };
+
+      "elm/url" = {
+        sha256 = "0av8x5syid40sgpl5vd7pry2rq0q4pga28b4yykn9gd9v12rs3l4";
+        version = "1.0.0";
+      };
+
+      "elm/virtual-dom" = {
+        sha256 = "0q1v5gi4g336bzz1lgwpn5b1639lrn63d8y6k6pimcyismp2i1yg";
+        version = "1.0.2";
+      };
+}
--- a/users/wpcarro/website/sandbox/learnpianochords/elm.json
+++ b/users/wpcarro/website/sandbox/learnpianochords/elm.json
@ -0,0 +1,30 @@
+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.1",
+    "dependencies": {
+        "direct": {
+            "elm/browser": "1.0.2",
+            "elm/core": "1.0.5",
+            "elm/html": "1.0.0",
+            "elm/random": "1.0.0",
+            "elm/svg": "1.0.1",
+            "elm/time": "1.0.0",
+            "elm-community/list-extra": "8.2.3",
+            "elm-community/maybe-extra": "5.2.0",
+            "elm-community/random-extra": "3.1.0"
+        },
+        "indirect": {
+            "elm/json": "1.1.3",
+            "elm/url": "1.0.0",
+            "elm/virtual-dom": "1.0.2",
+            "owanturist/elm-union-find": "1.0.0"
+        }
+    },
+    "test-dependencies": {
+        "direct": {},
+        "indirect": {}
+    }
+}
--- a/users/wpcarro/website/sandbox/learnpianochords/ideas.org
+++ b/users/wpcarro/website/sandbox/learnpianochords/ideas.org
@ -0,0 +1,3 @@
+* Support a frequency table of all of the chords
+* Support using spaced-repetition to help populate the frequency table of chords
+* If doing a frequency table, support left and right hands
--- a/users/wpcarro/website/sandbox/learnpianochords/index.css
+++ b/users/wpcarro/website/sandbox/learnpianochords/index.css
@ -0,0 +1,3 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
--- a/users/wpcarro/website/sandbox/learnpianochords/index.html
+++ b/users/wpcarro/website/sandbox/learnpianochords/index.html
@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>Learn Piano Chords</title>
+    <link rel="stylesheet" href="./output.css" />
+    <script src="./Main.min.js"></script>
+  </head>
+  <body class="font-serif">
+    <div id="mount"></div>
+    <script>
+     Elm.Main.init({node: document.getElementById("mount")});
+    </script>
+  </body>
+</html>
--- a/users/wpcarro/website/sandbox/learnpianochords/registry.dat
+++ b/users/wpcarro/website/sandbox/learnpianochords/registry.dat
--- a/users/wpcarro/website/sandbox/learnpianochords/shell.nix
+++ b/users/wpcarro/website/sandbox/learnpianochords/shell.nix
@ -0,0 +1,10 @@
+let
+  briefcase = import <briefcase> {};
+  pkgs = briefcase.third_party.pkgs;
+in pkgs.mkShell {
+  buildInputs = with pkgs.elmPackages; [
+    elm
+    elm-format
+    elm-live
+  ];
+}
--- a/users/wpcarro/website/sandbox/learnpianochords/src/FlashCard.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/FlashCard.elm
@ -0,0 +1,42 @@
+module FlashCard exposing (render)
+
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Responsive
+import State
+import Tailwind
+import Theory
+
+
+render :
+    { chord : Theory.Chord
+    , visible : Bool
+    }
+    -> Html State.Msg
+render { chord, visible } =
+    let
+        classes =
+            [ "bg-white"
+            , "fixed"
+            , "top-0"
+            , "left-0"
+            , "z-30"
+            , "w-screen"
+            , "h-screen"
+            , Tailwind.if_ visible "opacity-100" "opacity-0"
+            ]
+    in
+    button
+        [ classes |> Tailwind.use |> class ]
+        [ h1
+            [ [ "text-center"
+              , "transform"
+              , "-rotate-90"
+              , Responsive.h1
+              ]
+                |> Tailwind.use
+                |> class
+            ]
+            [ text (Theory.viewChord chord) ]
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Icon.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Icon.elm
@ -0,0 +1,44 @@
+module Icon exposing (..)
+
+import Svg exposing (node, svg)
+import Svg.Attributes exposing (..)
+import UI
+
+
+svgColor color =
+    let
+        classes =
+            case color of
+                UI.Primary ->
+                    [ "text-gray-500", "fill-current" ]
+
+                UI.Secondary ->
+                    [ "text-gray-300", "fill-current" ]
+    in
+    class <| String.join " " classes
+
+
+cog =
+    svg [ class "icon-cog", viewBox "0 0 24 24", xmlLang "http://www.w3.org/2000/svg" ]
+        [ Svg.path
+            [ svgColor UI.Primary
+            , d "M6.8 3.45c.87-.52 1.82-.92 2.83-1.17a2.5 2.5 0 0 0 4.74 0c1.01.25 1.96.65 2.82 1.17a2.5 2.5 0 0 0 3.36 3.36c.52.86.92 1.8 1.17 2.82a2.5 2.5 0 0 0 0 4.74c-.25 1.01-.65 1.96-1.17 2.82a2.5 2.5 0 0 0-3.36 3.36c-.86.52-1.8.92-2.82 1.17a2.5 2.5 0 0 0-4.74 0c-1.01-.25-1.96-.65-2.82-1.17a2.5 2.5 0 0 0-3.36-3.36 9.94 9.94 0 0 1-1.17-2.82 2.5 2.5 0 0 0 0-4.74c.25-1.01.65-1.96 1.17-2.82a2.5 2.5 0 0 0 3.36-3.36zM12 16a4 4 0 1 0 0-8 4 4 0 0 0 0 8z"
+            , fill "red"
+            ]
+            []
+        , node "circle"
+            [ svgColor UI.Secondary, cx "12", cy "12", r "2" ]
+            []
+        ]
+
+
+close =
+    svg [ class "icon-close", viewBox "0 0 24 24", xmlLang "http://www.w3.org/2000/svg" ]
+        [ Svg.path
+            [ svgColor UI.Primary
+            , d "M15.78 14.36a1 1 0 0 1-1.42 1.42l-2.82-2.83-2.83 2.83a1 1 0 1 1-1.42-1.42l2.83-2.82L7.3 8.7a1 1 0 0 1 1.42-1.42l2.83 2.83 2.82-2.83a1 1 0 0 1 1.42 1.42l-2.83 2.83 2.83 2.82z"
+            , fill "red"
+            , fillRule "evenodd"
+            ]
+            []
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Main.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Main.elm
@ -0,0 +1,44 @@
+module Main exposing (main)
+
+import Browser
+import Html exposing (..)
+import Misc
+import Overview
+import Practice
+import Preferences
+import State
+import Time exposing (..)
+
+
+subscriptions : State.Model -> Sub State.Msg
+subscriptions model =
+    if model.isPaused then
+        Sub.none
+
+    else
+        Sub.batch
+            [ Time.every (model.tempo * 2 |> Misc.bpmToMilliseconds |> toFloat) (\_ -> State.ToggleFlashCard)
+            , Time.every (model.tempo |> Misc.bpmToMilliseconds |> toFloat) (\_ -> State.NextChord)
+            ]
+
+
+view : State.Model -> Html State.Msg
+view model =
+    case model.view of
+        State.Preferences ->
+            Preferences.render model
+
+        State.Practice ->
+            Practice.render model
+
+        State.Overview ->
+            Overview.render model
+
+
+main =
+    Browser.element
+        { init = \() -> ( State.init, Cmd.none )
+        , subscriptions = subscriptions
+        , update = State.update
+        , view = view
+        }
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Misc.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Misc.elm
@ -0,0 +1,59 @@
+module Misc exposing (..)
+
+import Array exposing (Array)
+
+
+comesAfter : a -> List a -> Maybe a
+comesAfter x xs =
+    case xs of
+        [] ->
+            Nothing
+
+        _ :: [] ->
+            Nothing
+
+        y :: z :: rest ->
+            if y == x then
+                Just z
+
+            else
+                comesAfter x (z :: rest)
+
+
+comesBefore : a -> List a -> Maybe a
+comesBefore x xs =
+    case xs of
+        [] ->
+            Nothing
+
+        _ :: [] ->
+            Nothing
+
+        y :: z :: rest ->
+            if z == x then
+                Just y
+
+            else
+                comesBefore x (z :: rest)
+
+
+find : (a -> Bool) -> List a -> Maybe a
+find pred xs =
+    case xs |> List.filter pred of
+        [] ->
+            Nothing
+
+        x :: _ ->
+            Just x
+
+
+{-| Return the number of milliseconds that elapse during an interval in a
+`target` bpm.
+-}
+bpmToMilliseconds : Int -> Int
+bpmToMilliseconds target =
+    let
+        msPerMinute =
+            1000 * 60
+    in
+    round (toFloat msPerMinute / toFloat target)
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Overview.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Overview.elm
@ -0,0 +1,122 @@
+module Overview exposing (render)
+
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Responsive
+import State
+import Tailwind
+import UI
+
+
+header1 : String -> Html msg
+header1 copy =
+    h2
+        [ [ "text-center"
+          , "pt-24"
+          , "pb-12"
+          , Responsive.h1
+          ]
+            |> Tailwind.use
+            |> class
+        ]
+        [ text copy ]
+
+
+header2 : String -> Html msg
+header2 copy =
+    h2
+        [ [ "text-center"
+          , "pb-10"
+          , Responsive.h2
+          ]
+            |> Tailwind.use
+            |> class
+        ]
+        [ text copy ]
+
+
+paragraph : String -> Html msg
+paragraph copy =
+    p
+        [ [ "pb-10"
+          , Responsive.h3
+          ]
+            |> Tailwind.use
+            |> class
+        ]
+        [ text copy ]
+
+
+sect : { title : String, copy : List String } -> Html msg
+sect { title, copy } =
+    section [] (header2 title :: (copy |> List.map paragraph))
+
+
+numberedList : List String -> Html msg
+numberedList items =
+    ol
+        [ [ "list-inside"
+          , "list-decimal"
+          , Responsive.h3
+          ]
+            |> Tailwind.use
+            |> class
+        ]
+        (items |> List.map (\x -> li [ [ "pb-10" ] |> Tailwind.use |> class ] [ text x ]))
+
+
+render : State.Model -> Html State.Msg
+render model =
+    div [ [ "container", "mx-auto" ] |> Tailwind.use |> class ]
+        [ header1 "Welcome to LearnPianoChords.app!"
+        , paragraph """
+                     Learn Piano Chords helps piano players master chords.
+                     """
+        , paragraph """
+                     Chords are the building blocks songwriters use to create
+                     music. Whether you're a performer or songwriter, you need
+                     to understand chords to unlock your full musical potential.
+                     """
+        , paragraph """
+                     I think that if practicing is enjoyable, students will
+                     practice more. Practice doesn’t make perfect; perfect
+                     practice makes perfect.
+                     """
+        , section []
+            [ header2 "Ready to get started?"
+            , numberedList
+                [ """
+                   Sit down at the piano.
+                   """
+                , """
+                   Set the tempo at which you would like to practice.
+                   """
+                , """
+                   Select the key or keys in which you would like to
+                   practice.
+                   """
+                , """
+                   When you are ready, close the preferences pane. We will show
+                   you the name of a chord, and you should play that chord on
+                   the piano.
+                 """
+                , """
+                   If you don't know how to play the chord, toggle the piano
+                   viewer to see the notes.
+                   """
+                , """
+                   At any point while you're training, press the screen to pause
+                   or resume your practice.
+                   """
+                ]
+            ]
+        , div [ [ "text-center", "py-20" ] |> Tailwind.use |> class ]
+            [ UI.simpleButton
+                { label = "Let's get started"
+                , handleClick = State.SetView State.Preferences
+                , color = UI.Secondary
+                , classes = []
+                }
+            ]
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Piano.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Piano.elm
@ -0,0 +1,194 @@
+module Piano exposing (render)
+
+import Browser
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import List.Extra
+import Theory
+import UI
+
+
+type alias KeyMarkup a =
+    { offset : Int
+    , isHighlit : Bool
+    , note : Theory.Note
+    , isRootNote : Bool
+    }
+    -> Html a
+
+
+type alias Props =
+    { chord : Maybe Theory.Chord
+    , firstNote : Theory.Note
+    , lastNote : Theory.Note
+    }
+
+
+naturalThickness : Int
+naturalThickness =
+    105
+
+
+accidentalThickness : Int
+accidentalThickness =
+    round (toFloat naturalThickness / 2.0)
+
+
+{-| Convert an integer into its pixel representation for CSS.
+-}
+pixelate : Int -> String
+pixelate x =
+    String.fromInt x ++ "px"
+
+
+{-| Return the markup for either a white or a black key.
+-}
+pianoKey : KeyMarkup a
+pianoKey { offset, isHighlit, note, isRootNote } =
+    let
+        { natColor, accColor, hiColor, rootColor } =
+            { natColor = "bg-white"
+            , accColor = "bg-black"
+            , hiColor = "bg-red-400"
+            , rootColor = "bg-red-600"
+            }
+
+        sharedClasses =
+            [ "box-border"
+            , "absolute"
+            , "border"
+            , "border-black"
+            ]
+
+        { keyLength, keyThickness, keyColor, offsetEdge, extraClasses } =
+            case Theory.keyClass note of
+                Theory.Natural ->
+                    { keyLength = "w-screen"
+                    , keyThickness = naturalThickness
+                    , keyColor = natColor
+                    , offsetEdge = "top"
+                    , extraClasses = []
+                    }
+
+                Theory.Accidental ->
+                    { keyLength = "w-2/3"
+                    , keyThickness = accidentalThickness
+                    , keyColor = accColor
+                    , offsetEdge = "top"
+                    , extraClasses = [ "z-10" ]
+                    }
+    in
+    div
+        [ class
+            (case ( isHighlit, isRootNote ) of
+                ( False, _ ) ->
+                    keyColor
+
+                ( True, True ) ->
+                    rootColor
+
+                ( True, False ) ->
+                    hiColor
+            )
+        , class keyLength
+        , style "height" (pixelate keyThickness)
+        , style offsetEdge (String.fromInt offset ++ "px")
+        , class <| String.join " " (List.concat [ sharedClasses, extraClasses ])
+        ]
+        []
+
+
+{-| A section of the piano consisting of all twelve notes.
+-}
+keys :
+    { start : Theory.Note
+    , end : Theory.Note
+    , highlitNotes : List Theory.Note
+    , rootNote : Maybe Theory.Note
+    }
+    -> List (Html a)
+keys { start, end, highlitNotes, rootNote } =
+    let
+        isHighlit note =
+            List.member note highlitNotes
+
+        spacing prevOffset prev curr =
+            case ( Theory.keyClass prev, Theory.keyClass curr ) of
+                ( Theory.Natural, Theory.Accidental ) ->
+                    prevOffset + naturalThickness - round (toFloat accidentalThickness / 2)
+
+                ( Theory.Accidental, Theory.Natural ) ->
+                    prevOffset + round (toFloat accidentalThickness / 2)
+
+                ( Theory.Natural, Theory.Natural ) ->
+                    prevOffset + naturalThickness
+
+                -- This pattern should never hit.
+                _ ->
+                    prevOffset
+
+        ( _, _, notes ) =
+            Theory.notesFromRange start end
+                |> List.reverse
+                |> List.foldl
+                    (\curr ( prevOffset, prev, result ) ->
+                        case ( prevOffset, prev ) of
+                            ( Nothing, Nothing ) ->
+                                ( Just 0
+                                , Just curr
+                                , pianoKey
+                                    { offset = 0
+                                    , isHighlit = List.member curr highlitNotes
+                                    , note = curr
+                                    , isRootNote =
+                                        rootNote
+                                            |> Maybe.map (\x -> x == curr)
+                                            |> Maybe.withDefault False
+                                    }
+                                    :: result
+                                )
+
+                            ( Just po, Just p ) ->
+                                let
+                                    offset =
+                                        spacing po p curr
+                                in
+                                ( Just offset
+                                , Just curr
+                                , pianoKey
+                                    { offset = offset
+                                    , isHighlit = List.member curr highlitNotes
+                                    , note = curr
+                                    , isRootNote =
+                                        rootNote
+                                            |> Maybe.map (\x -> x == curr)
+                                            |> Maybe.withDefault False
+                                    }
+                                    :: result
+                                )
+
+                            -- This pattern should never hit.
+                            _ ->
+                                ( Nothing, Nothing, [] )
+                    )
+                    ( Nothing, Nothing, [] )
+    in
+    notes
+
+
+{-| Return the HTML that renders a piano representation.
+-}
+render : Props -> Html a
+render { chord } =
+    div [ style "display" "flex" ]
+        (keys
+            { start = Theory.G3
+            , end = Theory.C6
+            , rootNote = chord |> Maybe.map .note
+            , highlitNotes =
+                chord
+                    |> Maybe.andThen Theory.notesForChord
+                    |> Maybe.withDefault []
+            }
+        )
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Practice.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Practice.elm
@ -0,0 +1,61 @@
+module Practice exposing (render)
+
+import FlashCard
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Icon
+import Piano
+import State
+import Tailwind
+import Theory
+import UI
+
+
+openPreferences : Html State.Msg
+openPreferences =
+    button
+        [ class "w-48 h-48 absolute left-0 top-0 z-50"
+        , onClick (State.SetView State.Preferences)
+        ]
+        [ Icon.cog ]
+
+
+render : State.Model -> Html State.Msg
+render model =
+    let
+        ( handleClick, buttonText ) =
+            if model.isPaused then
+                ( State.Play, "Tap to practice" )
+
+            else
+                ( State.Pause, "" )
+    in
+    div []
+        [ openPreferences
+        , case model.selectedChord of
+            Just chord ->
+                FlashCard.render
+                    { chord = chord
+                    , visible = model.showFlashCard
+                    }
+
+            Nothing ->
+                -- Here I'm abusing the overlayButton component to render text
+                -- horizontally. I should support a UI component for this.
+                UI.overlayButton
+                    { label = "Get ready..."
+                    , handleClick = State.DoNothing
+                    , isVisible = True
+                    }
+        , UI.overlayButton
+            { label = buttonText
+            , handleClick = handleClick
+            , isVisible = model.isPaused
+            }
+        , Piano.render
+            { chord = model.selectedChord
+            , firstNote = model.firstNote
+            , lastNote = model.lastNote
+            }
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Preferences.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Preferences.elm
@ -0,0 +1,148 @@
+module Preferences exposing (render)
+
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Icon
+import Responsive
+import State
+import Tailwind
+import Tempo
+import Theory
+import UI
+
+
+selectKey :
+    State.Model
+    ->
+        { relativeMajor : Theory.Key
+        , relativeMinor : Theory.Key
+        }
+    -> Html State.Msg
+selectKey model { relativeMajor, relativeMinor } =
+    let
+        active key =
+            List.member key model.whitelistedKeys
+
+        buttonLabel major minor =
+            Theory.viewKey major ++ ", " ++ Theory.viewKey minor
+    in
+    div [ class "flex pt-0" ]
+        [ UI.textToggleButton
+            { label = buttonLabel relativeMajor relativeMinor
+            , handleClick = State.ToggleKey relativeMajor
+            , classes = [ "flex-1" ]
+            , toggled = active relativeMajor
+            }
+        ]
+
+
+inversionCheckboxes : State.Model -> Html State.Msg
+inversionCheckboxes model =
+    div []
+        [ h2
+            [ [ "text-gray-500"
+              , "text-center"
+              , "pt-10"
+              , Responsive.h2
+              ]
+                |> Tailwind.use
+                |> class
+            ]
+            [ text "Select inversions" ]
+        , ul
+            [ [ "flex", "justify-center" ] |> Tailwind.use |> class ]
+            (Theory.allInversions
+                |> List.map
+                    (\inversion ->
+                        li []
+                            [ UI.textToggleButton
+                                { label = Theory.inversionName inversion
+                                , handleClick = State.ToggleInversion inversion
+                                , classes = []
+                                , toggled = List.member inversion model.whitelistedInversions
+                                }
+                            ]
+                    )
+            )
+        ]
+
+
+keyCheckboxes : State.Model -> Html State.Msg
+keyCheckboxes model =
+    let
+        majorKey pitchClass =
+            { pitchClass = pitchClass, mode = Theory.MajorMode }
+
+        minorKey pitchClass =
+            { pitchClass = pitchClass, mode = Theory.MinorMode }
+
+        circleOfFifths =
+            [ ( Theory.C, Theory.A )
+            , ( Theory.G, Theory.E )
+            , ( Theory.D, Theory.B )
+            , ( Theory.A, Theory.F_sharp )
+            , ( Theory.E, Theory.C_sharp )
+            , ( Theory.B, Theory.G_sharp )
+            , ( Theory.F_sharp, Theory.D_sharp )
+            , ( Theory.C_sharp, Theory.A_sharp )
+            , ( Theory.G_sharp, Theory.F )
+            , ( Theory.D_sharp, Theory.C )
+            , ( Theory.A_sharp, Theory.G )
+            , ( Theory.F, Theory.D )
+            ]
+    in
+    div []
+        [ h2
+            [ [ "text-gray-500"
+              , "text-center"
+              , "pt-10"
+              , Responsive.h2
+              ]
+                |> Tailwind.use
+                |> class
+            ]
+            [ text "Select keys" ]
+        , ul []
+            (circleOfFifths
+                |> List.map
+                    (\( major, minor ) ->
+                        selectKey model
+                            { relativeMajor = majorKey major
+                            , relativeMinor = minorKey minor
+                            }
+                    )
+            )
+        ]
+
+
+closePreferences : Html State.Msg
+closePreferences =
+    button
+        [ [ "w-48"
+          , "lg:w-32"
+          , "h-48"
+          , "lg:h-32"
+          , "absolute"
+          , "right-0"
+          , "top-0"
+          , "z-10"
+          ]
+            |> Tailwind.use
+            |> class
+        , onClick (State.SetView State.Practice)
+        ]
+        [ Icon.close ]
+
+
+render : State.Model -> Html State.Msg
+render model =
+    div [ class "pt-10 pb-20 px-10" ]
+        [ closePreferences
+        , Tempo.render
+            { tempo = model.tempo
+            , handleInput = State.SetTempo
+            }
+        , inversionCheckboxes model
+        , keyCheckboxes model
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Responsive.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Responsive.elm
@ -0,0 +1,19 @@
+module Responsive exposing (..)
+
+{-| Returns a string containing all of the Tailwind selectors we use to size
+h2-sized elements across various devices. -}
+h1 : String
+h1 =
+    "text-6xl lg:text-4xl"
+
+{-| Returns a string containing all of the Tailwind selectors we use to size
+h2-sized elements across various devices. -}
+h2 : String
+h2 =
+    "text-5xl lg:text-3xl"
+
+{-| Returns a string containing all of the Tailwind selectors we use to size
+h3-sized elements across various devices. -}
+h3 : String
+h3 =
+    "text-4xl lg:text-2xl"
--- a/users/wpcarro/website/sandbox/learnpianochords/src/State.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/State.elm
@ -0,0 +1,179 @@
+module State exposing (..)
+
+import Random
+import Random.List
+import Theory
+
+
+type Msg
+    = NextChord
+    | NewChord Theory.Chord
+    | Play
+    | Pause
+    | SetTempo String
+    | ToggleInversion Theory.ChordInversion
+    | ToggleKey Theory.Key
+    | DoNothing
+    | SetView View
+    | ToggleFlashCard
+
+
+type View
+    = Preferences
+    | Practice
+    | Overview
+
+
+type alias Model =
+    { whitelistedChords : List Theory.Chord
+    , whitelistedChordTypes : List Theory.ChordType
+    , whitelistedInversions : List Theory.ChordInversion
+    , whitelistedPitchClasses : List Theory.PitchClass
+    , whitelistedKeys : List Theory.Key
+    , selectedChord : Maybe Theory.Chord
+    , isPaused : Bool
+    , tempo : Int
+    , firstNote : Theory.Note
+    , lastNote : Theory.Note
+    , view : View
+    , showFlashCard : Bool
+    }
+
+
+{-| The initial state for the application.
+-}
+init : Model
+init =
+    let
+        ( firstNote, lastNote ) =
+            ( Theory.C3, Theory.C6 )
+
+        inversions =
+            [ Theory.Root ]
+
+        chordTypes =
+            Theory.allChordTypes
+
+        pitchClasses =
+            Theory.allPitchClasses
+
+        keys =
+            [ { pitchClass = Theory.C, mode = Theory.MajorMode } ]
+    in
+    { whitelistedChords =
+        keys
+            |> List.concatMap Theory.chordsForKey
+            |> List.filter (\chord -> List.member chord.chordInversion inversions)
+    , whitelistedChordTypes = chordTypes
+    , whitelistedInversions = inversions
+    , whitelistedPitchClasses = pitchClasses
+    , whitelistedKeys = keys
+    , selectedChord = Nothing
+    , isPaused = True
+    , tempo = 10
+    , firstNote = firstNote
+    , lastNote = lastNote
+    , view = Overview
+    , showFlashCard = True
+    }
+
+
+{-| Now that we have state, we need a function to change the state.
+-}
+update : Msg -> Model -> ( Model, Cmd Msg )
+update msg model =
+    case msg of
+        DoNothing ->
+            ( model, Cmd.none )
+
+        SetView x ->
+            ( { model
+                | view = x
+                , isPaused = True
+              }
+            , Cmd.none
+            )
+
+        NewChord chord ->
+            ( { model | selectedChord = Just chord }
+            , Cmd.none
+            )
+
+        NextChord ->
+            ( model
+            , Random.generate
+                (\x ->
+                    case x of
+                        ( Just chord, _ ) ->
+                            NewChord chord
+
+                        ( Nothing, _ ) ->
+                            DoNothing
+                )
+                (Random.List.choose model.whitelistedChords)
+            )
+
+        Play ->
+            ( { model | isPaused = False }
+            , Cmd.none
+            )
+
+        Pause ->
+            ( { model | isPaused = True }
+            , Cmd.none
+            )
+
+        ToggleInversion inversion ->
+            let
+                inversions =
+                    if List.member inversion model.whitelistedInversions then
+                        List.filter ((/=) inversion) model.whitelistedInversions
+
+                    else
+                        inversion :: model.whitelistedInversions
+            in
+            ( { model
+                | whitelistedInversions = inversions
+                , whitelistedChords =
+                    model.whitelistedKeys
+                        |> List.concatMap Theory.chordsForKey
+                        |> List.filter (\chord -> List.member chord.chordInversion inversions)
+              }
+            , Cmd.none
+            )
+
+        ToggleKey key ->
+            let
+                keys =
+                    if List.member key model.whitelistedKeys then
+                        List.filter ((/=) key) model.whitelistedKeys
+
+                    else
+                        key :: model.whitelistedKeys
+            in
+            ( { model
+                | whitelistedKeys = keys
+                , whitelistedChords =
+                    keys
+                        |> List.concatMap Theory.chordsForKey
+                        |> List.filter (\chord -> List.member chord.chordInversion model.whitelistedInversions)
+                , selectedChord = Nothing
+              }
+            , Cmd.none
+            )
+
+        SetTempo tempo ->
+            ( { model
+                | tempo =
+                    case String.toInt tempo of
+                        Just x ->
+                            x
+
+                        Nothing ->
+                            model.tempo
+              }
+            , Cmd.none
+            )
+
+        ToggleFlashCard ->
+            ( { model | showFlashCard = not model.showFlashCard }, Cmd.none )
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Tailwind.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Tailwind.elm
@ -0,0 +1,29 @@
+module Tailwind exposing (..)
+
+{-| Functions to make Tailwind development in Elm even more pleasant.
+-}
+
+
+{-| Conditionally use `class` selection when `condition` is true.
+-}
+when : Bool -> String -> String
+when condition class =
+    if condition then
+        class
+
+    else
+        ""
+
+
+if_ : Bool -> String -> String -> String
+if_ condition whenTrue whenFalse =
+    if condition then
+        whenTrue
+
+    else
+        whenFalse
+
+
+use : List String -> String
+use styles =
+    String.join " " styles
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Tempo.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Tempo.elm
@ -0,0 +1,33 @@
+module Tempo exposing (render)
+
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Responsive
+import Tailwind
+import UI
+
+
+type alias Props msg =
+    { tempo : Int
+    , handleInput : String -> msg
+    }
+
+
+render : Props msg -> Html msg
+render { tempo, handleInput } =
+    div [ class "text-center" ]
+        [ p
+            [ [ "py-10"
+              , Responsive.h2
+              ]
+                |> Tailwind.use
+                |> class
+            ]
+            [ text (String.fromInt tempo ++ " BPM") ]
+        , UI.textField
+            { placeholderText = "Set tempo..."
+            , handleInput = handleInput
+            , classes = []
+            }
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/Theory.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/Theory.elm
--- a/users/wpcarro/website/sandbox/learnpianochords/src/UI.elm
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/UI.elm
@ -0,0 +1,159 @@
+module UI exposing (..)
+
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (..)
+import Responsive
+import Tailwind
+
+
+type Color
+    = Primary
+    | Secondary
+
+
+bgForColor : Color -> String
+bgForColor color =
+    case color of
+        Primary ->
+            "bg-gray-600"
+
+        Secondary ->
+            "bg-gray-300"
+
+
+textForColor : Color -> String
+textForColor color =
+    case color of
+        Primary ->
+            "text-white"
+
+        Secondary ->
+            "text-black"
+
+
+simpleButton :
+    { label : String
+    , handleClick : msg
+    , color : Color
+    , classes : List String
+    }
+    -> Html msg
+simpleButton { label, handleClick, color, classes } =
+    let
+        buttonClasses =
+            [ bgForColor color
+            , textForColor color
+            , "py-10"
+            , "lg:py-6"
+            , "px-20"
+            , "lg:px-12"
+            , "rounded-lg"
+            , Responsive.h2
+            ]
+    in
+    button
+        [ class (Tailwind.use <| List.concat [ buttonClasses, classes ])
+        , onClick handleClick
+        ]
+        [ text label ]
+
+
+textToggleButton :
+    { label : String
+    , handleClick : msg
+    , classes : List String
+    , toggled : Bool
+    }
+    -> Html msg
+textToggleButton { label, toggled, handleClick, classes } =
+    let
+        ( textColor, textTreatment ) =
+            if toggled then
+                ( "text-red-600", "underline" )
+
+            else
+                ( "text-black", "no-underline" )
+
+        buttonClasses =
+            [ textColor
+            , textTreatment
+            , "py-8"
+            , "lg:py-5"
+            , "px-10"
+            , "lg:px-6"
+            , Responsive.h2
+            ]
+    in
+    button
+        [ class (Tailwind.use <| List.concat [ buttonClasses, classes ])
+        , onClick handleClick
+        ]
+        [ text label ]
+
+
+textField :
+    { placeholderText : String
+    , handleInput : String -> msg
+    , classes : List String
+    }
+    -> Html msg
+textField { placeholderText, handleInput, classes } =
+    let
+        inputClasses =
+            [ "w-full"
+            , "py-10"
+            , "lg:py-6"
+            , "px-16"
+            , "lg:px-10"
+            , "border"
+            , "rounded-lg"
+            , Responsive.h2
+            ]
+    in
+    input
+        [ class (Tailwind.use <| List.concat [ inputClasses, classes ])
+        , onInput handleInput
+        , placeholder placeholderText
+        ]
+        []
+
+
+overlayButton :
+    { label : String
+    , handleClick : msg
+    , isVisible : Bool
+    }
+    -> Html msg
+overlayButton { label, handleClick, isVisible } =
+    let
+        classes =
+            [ "fixed"
+            , "top-0"
+            , "left-0"
+            , "block"
+            , "z-40"
+            , "w-screen"
+            , "h-screen"
+            , Tailwind.if_ isVisible "opacity-100" "opacity-0"
+            ]
+    in
+    button
+        [ classes |> Tailwind.use |> class
+        , style "background-color" "rgba(0,0,0,1.0)"
+        , onClick handleClick
+        ]
+        [ h1
+            [ style "-webkit-text-stroke-width" "2px"
+            , style "-webkit-text-stroke-color" "black"
+            , class <|
+                Tailwind.use
+                    [ "transform"
+                    , "-rotate-90"
+                    , "text-white"
+                    , "font-mono"
+                    , Responsive.h1
+                    ]
+            ]
+            [ text label ]
+        ]
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/.envrc
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/.envrc
@ -0,0 +1,6 @@
+source_up
+use_nix
+export SERVER_PORT=3000
+export CLIENT_PORT=8000
+export GOOGLE_CLIENT_ID="$(jq -j '.google | .clientId' < ~/briefcase/secrets.json)"
+export STRIPE_API_KEY="$(jq -j '.stripe | .apiKey' < ~/briefcase/secrets.json)"
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/.ghci
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/.ghci
@ -0,0 +1,7 @@
+:set prompt "> "
+:set -Wall
+
+:set -XOverloadedStrings
+:set -XNoImplicitPrelude
+:set -XRecordWildCards
+:set -XTypeApplications
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/API.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/API.hs
@ -0,0 +1,16 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeOperators #-}
+--------------------------------------------------------------------------------
+module API where
+--------------------------------------------------------------------------------
+import Servant.API
+
+import qualified Types as T
+--------------------------------------------------------------------------------
+
+type API = "verify"
+           :> ReqBody '[JSON] T.VerifyGoogleSignInRequest
+           :> Post '[JSON] NoContent
+      :<|> "create-payment-intent"
+           :> ReqBody '[JSON] T.PaymentIntent
+           :> Post '[JSON] T.CreatePaymentIntentResponse
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/App.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/App.hs
@ -0,0 +1,57 @@
+--------------------------------------------------------------------------------
+module App where
+--------------------------------------------------------------------------------
+import RIO hiding (Handler)
+import Servant
+import API
+import Data.String.Conversions (cs)
+import Control.Monad.IO.Class (liftIO)
+import Network.Wai.Middleware.Cors
+import GoogleSignIn (EncodedJWT(..), ValidationResult(..))
+import Utils
+
+import qualified Network.Wai.Handler.Warp as Warp
+import qualified GoogleSignIn
+import qualified Stripe
+import qualified Types as T
+--------------------------------------------------------------------------------
+
+server :: T.Context -> Server API
+server ctx@T.Context{..} = verifyGoogleSignIn
+                      :<|> createPaymentIntent
+  where
+    verifyGoogleSignIn :: T.VerifyGoogleSignInRequest -> Handler NoContent
+    verifyGoogleSignIn T.VerifyGoogleSignInRequest{..} = do
+      validationResult <- liftIO $ GoogleSignIn.validateJWT False (EncodedJWT idToken)
+      case validationResult of
+        Valid _ -> do
+          -- If GoogleLinkedAccounts has email from JWT:
+          --   create a new session for email
+          -- Else:
+          --   Redirect the SPA to the sign-up / payment page
+          pure NoContent
+        err -> do
+          throwError err401 { errBody = err |> GoogleSignIn.explainResult |> cs }
+
+    createPaymentIntent :: T.PaymentIntent -> Handler T.CreatePaymentIntentResponse
+    createPaymentIntent pmt = do
+      clientSecret <- liftIO $ Stripe.createPaymentIntent ctx pmt
+      pure T.CreatePaymentIntentResponse{..}
+
+run :: T.App
+run = do
+  ctx@T.Context{..} <- ask
+  ctx
+    |> server
+    |> serve (Proxy @ API)
+    |> cors (const $ Just corsPolicy)
+    |> Warp.run contextServerPort
+    |> liftIO
+  pure $ Right ()
+  where
+    corsPolicy :: CorsResourcePolicy
+    corsPolicy = simpleCorsResourcePolicy
+      { corsOrigins = Just (["http://localhost:8000"], True)
+      , corsMethods = simpleMethods ++ ["PUT", "PATCH", "DELETE", "OPTIONS"]
+      , corsRequestHeaders = simpleHeaders ++ ["Content-Type", "Authorization"]
+      }
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Fixtures.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Fixtures.hs
@ -0,0 +1,67 @@
+--------------------------------------------------------------------------------
+module Fixtures where
+--------------------------------------------------------------------------------
+import RIO
+import Web.JWT
+import Utils
+
+import qualified Data.Map as Map
+import qualified GoogleSignIn
+import qualified TestUtils
+import qualified Data.Time.Clock.POSIX as POSIX
+import qualified System.IO.Unsafe as Unsafe
+--------------------------------------------------------------------------------
+
+-- | These are the JWT fields that I'd like to overwrite in the `googleJWT`
+-- function.
+data JWTFields = JWTFields
+  { overwriteSigner :: Signer
+  , overwriteAuds :: [StringOrURI]
+  , overwriteIss :: StringOrURI
+  , overwriteExp :: NumericDate
+  }
+
+defaultJWTFields :: JWTFields
+defaultJWTFields = do
+  let tenDaysFromToday = POSIX.getPOSIXTime
+                         |> Unsafe.unsafePerformIO
+                         |> (\x -> x * 60 * 60 * 25 * 10)
+                         |> numericDate
+                         |> TestUtils.unsafeJust
+  JWTFields
+    { overwriteSigner = hmacSecret "secret"
+    , overwriteAuds = ["771151720060-buofllhed98fgt0j22locma05e7rpngl.apps.googleusercontent.com"]
+                      |> fmap TestUtils.unsafeStringOrURI
+    , overwriteIss = TestUtils.unsafeStringOrURI "accounts.google.com"
+    , overwriteExp = tenDaysFromToday
+    }
+
+googleJWT :: JWTFields -> GoogleSignIn.EncodedJWT
+googleJWT JWTFields{..} =
+  encodeSigned signer jwtHeader claimSet
+  |> GoogleSignIn.EncodedJWT
+  where
+    signer :: Signer
+    signer = overwriteSigner
+
+    jwtHeader :: JOSEHeader
+    jwtHeader = JOSEHeader
+      { typ = Just "JWT"
+      , cty = Nothing
+      , alg = Just RS256
+      , kid = Just "f05415b13acb9590f70df862765c655f5a7a019e"
+      }
+
+    claimSet :: JWTClaimsSet
+    claimSet = JWTClaimsSet
+      { iss = Just overwriteIss
+      , sub = stringOrURI "114079822315085727057"
+      , aud = overwriteAuds |> Right |> Just
+      -- TODO: Replace date creation with a human-readable date constructor.
+      , Web.JWT.exp = Just overwriteExp
+      , nbf = Nothing
+      -- TODO: Replace date creation with a human-readable date constructor.
+      , iat = numericDate 1596752853
+      , unregisteredClaims = ClaimsMap (Map.fromList [])
+      , jti = stringOrURI "0d3d7fa1fe05bedec0a91c88294936b2b4d1b13c"
+      }
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/GoogleSignIn.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/GoogleSignIn.hs
@ -0,0 +1,111 @@
+--------------------------------------------------------------------------------
+module GoogleSignIn where
+--------------------------------------------------------------------------------
+import RIO
+import Data.String.Conversions (cs)
+import Web.JWT
+import Utils
+
+import qualified Network.HTTP.Simple as HTTP
+import qualified Data.Text as Text
+import qualified Web.JWT as JWT
+import qualified Data.Time.Clock.POSIX as POSIX
+--------------------------------------------------------------------------------
+
+newtype EncodedJWT = EncodedJWT Text
+  deriving (Show)
+
+newtype DecodedJWT = DecodedJWT (JWT UnverifiedJWT)
+  deriving (Show)
+
+instance Eq DecodedJWT where
+  (DecodedJWT _) == (DecodedJWT _) = True
+
+data ValidationResult
+  = Valid DecodedJWT
+  | CannotDecodeJWT
+  | GoogleSaysInvalid Text
+  | NoMatchingClientIDs [StringOrURI]
+  | WrongIssuer StringOrURI
+  | StringOrURIParseFailure Text
+  | TimeConversionFailure
+  | MissingRequiredClaim Text
+  | StaleExpiry NumericDate
+  deriving (Eq, Show)
+
+-- | Returns True when the supplied `jwt` meets the following criteria:
+-- * The token has been signed by Google
+-- * The value of `aud` matches my Google client's ID
+-- * The value of `iss` matches is "accounts.google.com" or
+--   "https://accounts.google.com"
+-- * The `exp` time has not passed
+--
+-- Set `skipHTTP` to `True` to avoid making the network request for testing.
+validateJWT :: Bool
+           -> EncodedJWT
+           -> IO ValidationResult
+validateJWT skipHTTP (EncodedJWT encodedJWT) = do
+  case encodedJWT |> decode of
+    Nothing -> pure CannotDecodeJWT
+    Just jwt -> do
+      if skipHTTP then
+        continue jwt
+      else do
+        let request = "https://oauth2.googleapis.com/tokeninfo"
+                      |> HTTP.setRequestQueryString [ ( "id_token", Just (cs encodedJWT) ) ]
+        res <- HTTP.httpLBS request
+        if HTTP.getResponseStatusCode res /= 200 then
+          pure $ GoogleSaysInvalid (res |> HTTP.getResponseBody |> cs)
+        else
+          continue jwt
+  where
+    continue :: JWT UnverifiedJWT -> IO ValidationResult
+    continue jwt = do
+      let audValues :: [StringOrURI]
+          audValues = jwt |> claims |> auds
+          expectedClientID :: Text
+          expectedClientID = "771151720060-buofllhed98fgt0j22locma05e7rpngl.apps.googleusercontent.com"
+          expectedIssuers :: [Text]
+          expectedIssuers = [ "accounts.google.com"
+                            , "https://accounts.google.com"
+                            ]
+          mExpectedClientID :: Maybe StringOrURI
+          mExpectedClientID = stringOrURI expectedClientID
+          mExpectedIssuers :: Maybe [StringOrURI]
+          mExpectedIssuers = expectedIssuers |> traverse stringOrURI
+      case (mExpectedClientID, mExpectedIssuers) of
+        (Nothing, _) -> pure $ StringOrURIParseFailure expectedClientID
+        (_, Nothing) -> pure $ StringOrURIParseFailure (Text.unwords expectedIssuers)
+        (Just clientID, Just parsedIssuers) ->
+          -- TODO: Prefer reading clientID from a config. I'm thinking of the
+          -- AppContext type having my Configuration
+          if not $ clientID `elem` audValues then
+            pure $ NoMatchingClientIDs audValues
+          else
+            case (jwt |> claims |> iss, jwt |> claims |> JWT.exp) of
+              (Nothing, _) -> pure $ MissingRequiredClaim "iss"
+              (_, Nothing) -> pure $ MissingRequiredClaim "exp"
+              (Just jwtIssuer, Just jwtExpiry) ->
+                if not $ jwtIssuer `elem` parsedIssuers then
+                  pure $ WrongIssuer jwtIssuer
+                else do
+                  mCurrentTime <- POSIX.getPOSIXTime |> fmap numericDate
+                  case mCurrentTime of
+                    Nothing -> pure TimeConversionFailure
+                    Just currentTime ->
+                      if not $ currentTime <= jwtExpiry then
+                        pure $ StaleExpiry jwtExpiry
+                      else
+                        pure $ jwt |> DecodedJWT |> Valid
+
+-- | Attempt to explain the `ValidationResult` to a human.
+explainResult :: ValidationResult -> String
+explainResult (Valid _) = "Everything appears to be valid"
+explainResult CannotDecodeJWT = "We had difficulty decoding the provided JWT"
+explainResult (GoogleSaysInvalid x) = "After checking with Google, they claimed that the provided JWT was invalid: " ++ cs x
+explainResult (NoMatchingClientIDs audFields) = "None of the values in the `aud` field on the provided JWT match our client ID: " ++ show audFields
+explainResult (WrongIssuer issuer) = "The `iss` field in the provided JWT does not match what we expect: " ++ show issuer
+explainResult (StringOrURIParseFailure x) = "We had difficulty parsing values as URIs" ++ show x
+explainResult TimeConversionFailure = "We had difficulty converting the current time to a value we can use to compare with the JWT's `exp` field"
+explainResult (MissingRequiredClaim claim) = "Your JWT is missing the following claim: " ++ cs claim
+explainResult (StaleExpiry x) = "The `exp` field on your JWT has expired" ++ x |> show |> cs
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Main.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Main.hs
@ -0,0 +1,37 @@
+--------------------------------------------------------------------------------
+module Main where
+--------------------------------------------------------------------------------
+import RIO
+import Prelude (putStr, putStrLn)
+
+import qualified Types as T
+import qualified System.Envy as Envy
+import qualified App
+--------------------------------------------------------------------------------
+
+-- | Attempt to read environment variables from the system and initialize the
+-- Context data type for our application.
+getAppContext :: IO (Either String T.Context)
+getAppContext = do
+  mEnv <- Envy.decodeEnv
+  case mEnv of
+    Left err -> pure $ Left err
+    Right T.Env{..} -> pure $ Right T.Context
+      { contextGoogleClientID = envGoogleClientID
+      , contextStripeAPIKey = envStripeAPIKey
+      , contextServerPort = envServerPort
+      , contextClientPort = envClientPort
+      }
+
+main :: IO ()
+main = do
+  mContext <- getAppContext
+  case mContext of
+    Left err -> putStrLn err
+    Right ctx -> do
+      result <- runRIO ctx App.run
+      case result of
+        Left err -> do
+          putStr "Something went wrong when executing the application: "
+          putStrLn $ show err
+        Right _ -> putStrLn "The application successfully executed."
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Spec.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Spec.hs
@ -0,0 +1,74 @@
+--------------------------------------------------------------------------------
+module Spec where
+--------------------------------------------------------------------------------
+import RIO
+import Test.Hspec
+import Utils
+import Web.JWT (numericDate, decode)
+import GoogleSignIn (EncodedJWT(..), DecodedJWT(..), ValidationResult(..))
+
+import qualified GoogleSignIn
+import qualified Fixtures as F
+import qualified TestUtils
+import qualified Data.Time.Clock.POSIX as POSIX
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = hspec $ do
+  describe "GoogleSignIn" $
+    describe "validateJWT" $ do
+      let validateJWT' = GoogleSignIn.validateJWT True
+      it "returns a decode error when an incorrectly encoded JWT is used" $ do
+        validateJWT' (GoogleSignIn.EncodedJWT "rubbish") `shouldReturn` CannotDecodeJWT
+
+      it "returns validation error when the aud field doesn't match my client ID" $ do
+        let auds = ["wrong-client-id"]
+                   |> fmap TestUtils.unsafeStringOrURI
+            encodedJWT = F.defaultJWTFields { F.overwriteAuds = auds }
+                         |> F.googleJWT
+        validateJWT' encodedJWT `shouldReturn` NoMatchingClientIDs auds
+
+      it "returns validation success when one of the aud fields matches my client ID" $ do
+        let auds = ["wrong-client-id", "771151720060-buofllhed98fgt0j22locma05e7rpngl.apps.googleusercontent.com"]
+                   |> fmap TestUtils.unsafeStringOrURI
+            encodedJWT@(EncodedJWT jwt) =
+              F.defaultJWTFields { F.overwriteAuds = auds }
+              |> F.googleJWT
+            decodedJWT = jwt |> decode |> TestUtils.unsafeJust |> DecodedJWT
+        validateJWT' encodedJWT `shouldReturn` Valid decodedJWT
+
+      it "returns validation error when one of the iss field doesn't match accounts.google.com or https://accounts.google.com" $ do
+        let erroneousIssuer = TestUtils.unsafeStringOrURI "not-accounts.google.com"
+            encodedJWT = F.defaultJWTFields { F.overwriteIss = erroneousIssuer }
+                         |> F.googleJWT
+        validateJWT' encodedJWT `shouldReturn` WrongIssuer erroneousIssuer
+
+      it "returns validation success when the iss field matches accounts.google.com or https://accounts.google.com" $ do
+        let erroneousIssuer = TestUtils.unsafeStringOrURI "https://accounts.google.com"
+            encodedJWT@(EncodedJWT jwt) =
+              F.defaultJWTFields { F.overwriteIss = erroneousIssuer }
+              |> F.googleJWT
+            decodedJWT = jwt |> decode |> TestUtils.unsafeJust |> DecodedJWT
+        validateJWT' encodedJWT `shouldReturn` Valid decodedJWT
+
+      it "fails validation when the exp field has expired" $ do
+        let mErroneousExp = numericDate 0
+        case mErroneousExp of
+          Nothing -> True `shouldBe` False
+          Just erroneousExp -> do
+            let encodedJWT = F.defaultJWTFields { F.overwriteExp = erroneousExp }
+                             |> F.googleJWT
+            validateJWT' encodedJWT `shouldReturn` StaleExpiry erroneousExp
+
+      it "passes validation when the exp field is current" $ do
+        mFreshExp <- POSIX.getPOSIXTime
+                     |> fmap (\x -> x * 60 * 60 * 24 * 10) -- 10 days later
+                     |> fmap numericDate
+        case mFreshExp of
+          Nothing -> True `shouldBe` False
+          Just freshExp -> do
+            let encodedJWT@(EncodedJWT jwt) =
+                  F.defaultJWTFields { F.overwriteExp = freshExp }
+                  |> F.googleJWT
+                decodedJWT = jwt |> decode |> TestUtils.unsafeJust |> DecodedJWT
+            validateJWT' encodedJWT `shouldReturn` Valid decodedJWT
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Stripe.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Stripe.hs
@ -0,0 +1,29 @@
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE DataKinds #-}
+--------------------------------------------------------------------------------
+module Stripe where
+--------------------------------------------------------------------------------
+import RIO
+import Prelude (print)
+import Data.String.Conversions (cs)
+import Data.Aeson
+import Network.HTTP.Req
+
+import qualified Types as T
+--------------------------------------------------------------------------------
+
+endpoint :: Text -> Url 'Https
+endpoint slug =
+  https "api.stripe.com" /: "v1" /: slug
+
+post :: (FromJSON b) => Text -> Text -> T.PaymentIntent -> IO (JsonResponse b)
+post apiKey slug T.PaymentIntent{..} = runReq defaultHttpConfig $ do
+  let params = "amount" =: paymentIntentAmount
+            <> "currency" =: paymentIntentCurrency
+  req POST (endpoint slug) (ReqBodyUrlEnc params) jsonResponse (oAuth2Bearer (cs apiKey))
+
+createPaymentIntent :: T.Context -> T.PaymentIntent -> IO T.Secret
+createPaymentIntent T.Context{..} pmtIntent = do
+  res <- post contextStripeAPIKey "payment_intents" pmtIntent
+  let T.StripePaymentIntent{..} = responseBody res :: T.StripePaymentIntent
+  pure pmtIntentClientSecret
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/TestUtils.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/TestUtils.hs
@ -0,0 +1,17 @@
+--------------------------------------------------------------------------------
+module TestUtils where
+--------------------------------------------------------------------------------
+import RIO
+import Web.JWT
+import Data.String.Conversions (cs)
+--------------------------------------------------------------------------------
+
+unsafeStringOrURI :: String -> StringOrURI
+unsafeStringOrURI x =
+  case stringOrURI (cs x) of
+    Nothing -> error $ "Failed to convert to StringOrURI: " ++ x
+    Just res -> res
+
+unsafeJust :: Maybe a -> a
+unsafeJust Nothing = error "Attempted to force a Nothing to be a something"
+unsafeJust (Just x) = x
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Types.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Types.hs
@ -0,0 +1,146 @@
+--------------------------------------------------------------------------------G
+module Types where
+--------------------------------------------------------------------------------
+import RIO
+import Data.Aeson
+import Network.HTTP.Req
+import Web.Internal.HttpApiData (ToHttpApiData(..))
+import System.Envy (FromEnv, fromEnv, env)
+--------------------------------------------------------------------------------
+
+-- | Read from .envrc
+data Env = Env
+  { envGoogleClientID :: !Text
+  , envServerPort :: !Int
+  , envClientPort :: !Int
+  , envStripeAPIKey :: !Text
+  } deriving (Eq, Show)
+
+instance FromEnv Env where
+  fromEnv _ = do
+    envGoogleClientID <- env "GOOGLE_CLIENT_ID"
+    envStripeAPIKey <- env "STRIPE_API_KEY"
+    envServerPort <- env "SERVER_PORT"
+    envClientPort <- env "CLIENT_PORT"
+    pure Env {..}
+
+-- | Application context: a combination of Env and additional values.
+data Context = Context
+  { contextGoogleClientID :: !Text
+  , contextStripeAPIKey :: !Text
+  , contextServerPort :: !Int
+  , contextClientPort :: !Int
+  }
+
+-- | Top-level except for our application, as RIO recommends defining.
+type Failure = ()
+
+-- | When our app executes along the "happy path" this is the type of result it
+-- produces.
+type Success = ()
+
+-- | This is our application monad.
+type AppM = RIO Context
+
+-- | The concrete type of our application.
+type App = AppM (Either Failure Success)
+
+data VerifyGoogleSignInRequest = VerifyGoogleSignInRequest
+  { idToken :: !Text
+  } deriving (Eq, Show)
+
+instance FromJSON VerifyGoogleSignInRequest where
+  parseJSON = withObject "VerifyGoogleSignInRequest" $ \x -> do
+    idToken <- x .: "idToken"
+    pure VerifyGoogleSignInRequest{..}
+
+data GoogleLinkedAccount = GoogleLinkedAccount
+  {
+  -- { googleLinkedAccountUUID :: UUID
+  -- , googleLinkedAccountEmail :: Email
+  -- , googleLinkedAccountTsCreated :: Timestamp
+    googleLinkedAccountGivenName :: !(Maybe Text)
+  , googleLinkedAccountFamilyName :: !(Maybe Text)
+  , googleLinkedAccountFullName :: !(Maybe Text)
+  -- , googleLinkedAccountPictureURL :: URL
+  -- , googleLinkedAccountLocale :: Maybe Locale
+  } deriving (Eq, Show)
+
+data PayingCustomer = PayingCustomer
+  {
+  -- { payingCustomerAccountUUID :: UUID
+  -- , payingCustomerTsCreated :: Timestamp
+  } deriving (Eq, Show)
+
+data Session = Session
+  {
+  -- { sessionUUID :: UUID
+  -- , sessionAccountUUID :: UUID
+  -- , sessionTsCreated :: Timestamp
+  } deriving (Eq, Show)
+
+data CurrencyCode = USD
+  deriving (Eq, Show)
+
+instance ToJSON CurrencyCode where
+  toJSON USD = String "usd"
+
+instance FromJSON CurrencyCode where
+  parseJSON = withText "CurrencyCode" $ \x ->
+    case x of
+      "usd" -> pure USD
+      _ -> fail "Expected a valid currency code like: \"usd\""
+
+instance ToHttpApiData CurrencyCode where
+  toQueryParam USD = "usd"
+
+data PaymentIntent = PaymentIntent
+  { paymentIntentAmount :: !Int
+  , paymentIntentCurrency :: !CurrencyCode
+  } deriving (Eq, Show)
+
+instance ToJSON PaymentIntent where
+  toJSON PaymentIntent{..} =
+    object [ "amount" .= paymentIntentAmount
+           , "currency" .= paymentIntentCurrency
+           ]
+
+instance FromJSON PaymentIntent where
+  parseJSON = withObject "" $ \x -> do
+    paymentIntentAmount <- x .: "amount"
+    paymentIntentCurrency <- x .: "currency"
+    pure PaymentIntent{..}
+
+instance QueryParam PaymentIntent where
+  queryParam = undefined
+
+-- All applications have their secrets... Using the secret type ensures that no
+-- sensitive information will get printed to the screen.
+newtype Secret = Secret Text deriving (Eq)
+
+instance Show Secret where
+  show (Secret _) = "[REDACTED]"
+
+instance ToJSON Secret where
+  toJSON (Secret x) = toJSON x
+
+instance FromJSON Secret where
+  parseJSON = withText "Secret" $ \x -> pure $ Secret x
+
+data CreatePaymentIntentResponse = CreatePaymentIntentResponse
+  { clientSecret :: Secret
+  } deriving (Eq, Show)
+
+instance ToJSON CreatePaymentIntentResponse where
+  toJSON CreatePaymentIntentResponse{..} =
+    object [ "clientSecret" .= clientSecret
+           ]
+
+data StripePaymentIntent = StripePaymentIntent
+  { pmtIntentClientSecret :: Secret
+  } deriving (Eq, Show)
+
+instance FromJSON StripePaymentIntent where
+  parseJSON = withObject "StripeCreatePaymentIntentResponse" $ \x -> do
+    pmtIntentClientSecret <- x .: "client_secret"
+    pure StripePaymentIntent{..}
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/Utils.hs
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/Utils.hs
@ -0,0 +1,8 @@
+--------------------------------------------------------------------------------
+module Utils where
+--------------------------------------------------------------------------------
+import Data.Function ((&))
+--------------------------------------------------------------------------------
+
+(|>) :: a -> (a -> b) -> b
+(|>) = (&)
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/default.nix
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/default.nix
@ -0,0 +1,28 @@
+let
+  briefcase = import <briefcase> {};
+in briefcase.buildHaskell.program {
+  name = "server";
+  srcs = builtins.path {
+    path = ./.;
+    name = "LearnPianoChords-server-src";
+  };
+  ghcExtensions = [
+    "OverloadedStrings"
+    "NoImplicitPrelude"
+    "RecordWildCards"
+    "TypeApplications"
+  ];
+  deps = hpkgs: with hpkgs; [
+    servant-server
+    aeson
+    wai-cors
+    warp
+    jwt
+    unordered-containers
+    base64
+    http-conduit
+    rio
+    envy
+    req
+  ];
+}
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/index.html
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/index.html
@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>Google Sign-in</title>
+    <script src="https://apis.google.com/js/platform.js" async defer></script>
+    <meta name="google-signin-client_id" content="771151720060-buofllhed98fgt0j22locma05e7rpngl.apps.googleusercontent.com">
+  </head>
+  <body>
+    <div class="g-signin2" data-onsuccess="onSignIn"></div>
+    <a href="#" onclick="signOut();">Sign out</a>
+    <script>
+     function onSignIn(googleUser) {
+       var idToken = googleUser.getAuthResponse().id_token;
+       fetch('http://localhost:3000/verify', {
+         method: 'POST',
+         headers: {
+           'Content-Type': 'application/json',
+         },
+         body: JSON.stringify({
+           idToken: idToken,
+         })
+       })
+         .then(x => console.log(x))
+         .catch(err => console.error(err));
+     }
+     function signOut() {
+       var auth2 = gapi.auth2.getAuthInstance();
+       auth2.signOut().then(function () {
+         console.log('User signed out.');
+       });
+     }
+    </script>
+  </body>
+</html>
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/init.sql
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/init.sql
@ -0,0 +1,41 @@
+BEGIN TRANSACTION;
+
+DROP TABLE IF EXISTS GoogleLinkedAccounts;
+DROP TABLE IF EXISTS PayingCustomers;
+DROP TABLE IF EXISTS Sessions;
+
+-- Store some of the information that Google provides to us from the JWT.
+CREATE TABLE GoogleLinkedAccounts (
+  accountUUID TEXT CHECK(LENGTH(uuid) == 36) NOT NULL UNIQUE,
+  email TEXT NOT NULL UNIQUE,
+  tsCreated TEXT NOT NULL, -- 'YYYY-MM-DD HH:MM:SS'
+  givenName TEXT,
+  familyName TEXT,
+  fullName TEXT,
+  pictureURL TEXT,
+  locale TEXT,
+  PRIMARY KEY (accountUUID)
+);
+
+-- Track which of our customers have a paid account.
+-- Defines a one-to-one relationship between:
+--   GoogleLinkedAccounts and PayingCustomers
+CREATE TABLE PayingCustomers (
+  accountUUID TEXT,
+  tsCreated TEXT,
+  PRIMARY KEY (accountUUID),
+  FOREIGN KEY (accountUUID) REFERENCES GoogleLinkedAccounts ON DELETE CASCADE
+);
+
+-- Define mobile and web sessions for our users.
+-- Defines a one-to-many relationship between:
+--   GoogleLinkedAccounts and Sessions
+CREATE TABLE Sessions (
+  sessionUUID TEXT CHECK(LENGTH(sessionUUID) == 36) NOT NULL UNIQUE,
+  accountUUID TEXT,
+  tsCreated TEXT NOT NULL, -- 'YYYY-MM-DD HH:MM:SS'
+  PRIMARY KEY (sessionUUID)
+  FOREIGN KEY(accountUUID) REFERENCES GoogleLinkedAccounts ON DELETE CASCADE
+);
+
+COMMIT;
--- a/users/wpcarro/website/sandbox/learnpianochords/src/server/shell.nix
+++ b/users/wpcarro/website/sandbox/learnpianochords/src/server/shell.nix
@ -0,0 +1,18 @@
+let
+  briefcase = import <briefcase> {};
+in briefcase.buildHaskell.shell {
+  deps = hpkgs: with hpkgs; [
+    hspec
+    servant-server
+    aeson
+    wai-cors
+    warp
+    jwt
+    unordered-containers
+    base64
+    http-conduit
+    rio
+    envy
+    req
+  ];
+}
--- a/users/wpcarro/website/sandbox/typo-po/README.md
+++ b/users/wpcarro/website/sandbox/typo-po/README.md
@ -0,0 +1,10 @@
+# Typo-po
+
+Have you ever published a blog post with typos? Or perhaps you've shared a blog
+post draft with a group of friends to solicit their feedback. If anyone reads
+your blog post and finds places where they can correct your typos or suggest
+grammatical improvements they can use typo-po.
+
+## What's with the name?
+
+We police your typos. We prefer po-po to police though. Send us donuts.