test/style.css
body {
  margin: 0;
}

html {
  fill: currentColor;
  font-family:
    system-ui,
    -apple-system,
    BlinkMacSystemFont,
    'Segoe UI',
    'Roboto',
    'Oxygen',
    'Ubuntu',
    'Cantarell',
    'Fira Sans',
    'Droid Sans',
    'Helvetica Neue',
    sans-serif;
  height: 100%;
  width: 100%;
}

body {
  --hue: 210;
  --on-primary: hsl(var(--hue, 212), 0%, 95%);
  --primary: hsl(var(--hue, 212), 40%, 50%);
  --surface: #fafafa;
  --surface-border: #fff;
  --on-surface: hsl(var(--hue, 212), 19%, 26%);

  --secondary-surface: hsl(0, 0%, 99.5%);
  --secondary-surface-border: hsl(0, 0%, 93%);
  --link: hsl(var(--hue, 212), 100%, 40%);

  --editable: #fff;
  --editable-border: #ddd;
  --on-editable: #333;

  background: var(--surface);
  color: var(--on-surface);
}

h2 {
  font-size: 24px;
  font-weight: 600;
  line-height: 0.7;
  padding-top: 1em;
  padding-bottom: 1em;
  border: none;
}
h3 {
  font-weight: 600;
  line-height: 0.7;
  margin-top: 3em;
  margin-bottom: 2em;
}

h4 {
  margin-top: 2em;
  margin-bottom: 1.5em;
}

h3 strong,
h4 strong {
  color: var(--primary, hsl(var(--hue, 212), 40%, 50%));
}

h4 {
  font-weight: 400;
}
/* h2, h3 {
  background: linear-gradient(#eee, #333);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
} */
main {
  padding-top: 1rem;
  width: 640px;
  max-width: 100vw;
  display: flex;
  align-items: flex-start;
  flex-flow: column wrap;
  margin: auto;
}
main > div {
  width: 100%;
}

main > div.frame {
  margin-top: 2em;
  padding-left: 1em;
  padding-right: 1em;
  width: calc(100% - 2em);
  margin-bottom: 4em;
  background: var(--secondary-surface);
  border: 1px solid var(--secondary-surface-border);
  border-radius: 8px;
}

kbd {
  font-family: Consolas, Monaco, 'Andale Mono', monospace;
  background: #f4f4f4;
  color: #333;
  padding: 1px 5px;
  border-radius: 5px;
}

.centered {
  display: flex;
  flex-flow: column;
  align-items: center;
  justify-content: center;
}

.links {
  display: flex;
  justify-content: space-around;
  padding-top: 1em;
  padding-bottom: 2em;
  width: 100%;
  font-size: 24px;
}
@media only screen and (max-width: 512px) {
  .links {
    font-size: 16px;
  }
}

.output {
  margin: 10px 0 10px 0;
  border-radius: 5px;
  border: 1px solid #333;

  min-height: 1em;
  padding: 5px;
  padding-top: 0.5em;
  padding-bottom: 0.5em;
  width: calc(100% - 10px); /* Subtract horizontal padding */

  font-family: 'IBM Plex mono', 'Source Code Pro', Menlo,
    'Bitstream Vera Sans Mono', Monaco, Courier, 'Andale Mono', monospace;
  color: #f0c674;

  background: #35434e;
  word-break: break-word;
  white-space: pre-wrap;
}

.output > div {
  white-space: pre-wrap;
  margin-bottom: 1em;
}

.output > div:last-child {
  margin-bottom: 0;
}

/* input,
textarea {
  border: 1px solid var(--editable-border);
  border-radius: 5px;
  background: var(--editable);
  color: var(--on-editable);
  padding: 5px;
} */

input::placeholder {
  opacity: 0.5;
}

.fa-w-24 {
  width: 24px;
  vertical-align: -5px;
}

a,
a:visited,
a:active {
  text-decoration: none;
  color: var(--link);
  border-radius: 1em;
  border: 1px solid transparent;
}

.links a {
  padding-left: 1em;
  padding-right: 1em;
  padding-top: 5px;
  padding-bottom: 5px;
}
.links a:visited:hover,
.links a:hover {
  border: 1px solid var(--secondary-surface-border);
  background: var(--surface);
}

a:hover {
  text-decoration: underline;
}
.links a:hover {
  text-decoration: none;
}

body > header {
  /* background-color: var(--primary, hsl(var(--hue, 212), 40%, 50%)); */
  height: 150px;
  max-width: 640px;
  margin: auto;
  display: flex;
  flex-flow: column;
  justify-content: center;
  align-items: flex-start;

  /* box-shadow: 16px 6px 24px rgba(0, 0, 0, 0.2); */
}

header > ul {
  display: flex;
  list-style-type: none;
  width: calc(100% - 16px);
  margin: 0;
  padding: 8px;
  border-radius: 8px;
  background: #eaeaea;
  border: 1px solid #ddd;
  gap: 0.5em;
}

header > ul > li {
  /* min-width: 100px; */
  width: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 10px;
}

header > ul > li:hover {
  background: #ddd;
}

header > ul > li.current {
  border-radius: inherit;
  background: #fff;
}

header > ul > li > a {
  padding-right: 8px;
  padding-left: 8px;
  padding-top: 0.5em;
  padding-bottom: 0.5em;
  font-weight: 600;
}

header > ul > li.current > a {
  color: var(--on-surface);
  /* border-radius: 0; */
  /* border-bottom: 2px solid var(--primary); */
}

header > ul > li > a:hover,
header > ul > li > a:visited,
header > ul > li > a:active {
  text-decoration: none;
}

/* header > ul > li.current > a,
header > ul > li.current > a:hover,
header > ul > li.current > a:visited,
header > ul > li.current > a:active {
  border-radius: inherit;
  background: #fff;
} */

header h1 {
  /* font-size: 3rem; */
  /* color: var(--on-primary); */
  margin-left: auto;
  margin-right: auto;
  max-width: 1024px;
  width: 640px;
  margin: auto;

  text-align: left;
  font-weight: 900;
  letter-spacing: 0.004em;
  text-transform: uppercase;
  letter-spacing: -0.04ex;
  text-rendering: optimizeLegibility;
  line-height: 0.9;
}

footer {
  margin-top: 5em;
  margin-bottom: 5em;
  text-align: center;

  display: flex;
  justify-content: center;
  flex-flow: column wrap;
}

footer a,
footer a:visited,
footer a:active {
  font-size: 18px;
  padding-top: 6px;
  padding-bottom: 6px;
}

math-field:not(:defined) {
  visibility: hidden;
}

/* math-field:focus-within {
outline: none;
background: red;
} */

code {
  white-space: pre-wrap;
}

h2 {
  font-size: 1em;
  padding: 0;
  margin: 0;
  color: #666;
}

#mathfield-container {
  padding: 8px;
  min-width: 50px;
  border: 1px solid #ddd;
}

#ta {
  font-size: 1.5em;
  font-weight: 700;
}

#find-input,
#replace-input {
  width: 320px;
}

.hidden {
  display: none;
}

.label {
  font-weight: 700;
}

.math {
  display: none;
}

/* .buttonbar button { */
button {
  font-weight: 600;
  font-size: 1rem;
  background: none;
  border: 1px solid rgba(0, 0, 0, 0.12);
  border-radius: 4px;
  color: #0066ce;
  fill: currentColor;
  position: relative;
  height: 2.5rem;
  line-height: 2.5rem;
  margin: 0;
  min-width: 120px;
  padding: 0 16px;
  display: inline-block;
  overflow: hidden;
  will-change: box-shadow;
  transition:
    box-shadow 0.2s cubic-bezier(0.4, 0, 1, 1),
    background-color 0.2s cubic-bezier(0.4, 0, 0.2, 1),
    color 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  outline: none;
  cursor: pointer;
  text-decoration: none;
  text-align: center;
  vertical-align: middle;
  -webkit-user-select: none;
  user-select: none;

  /* font-size: 16px;
  letter-spacing: 0.08929em;
  text-transform: uppercase;
  box-shadow: 0 1px 5px 0 rgba(0, 0, 0, 0.2), 0 2px 2px 0 rgba(0, 0, 0, 0.14),
    0 3px 1px -2px rgba(0, 0, 0, 0.12); */
}

button:first-child {
  margin-left: 0;
}

button:hover {
  background-color: rgba(0, 0, 0, 0.08);
}

button:active {
  background-color: white;
}

button.primary,
button.active {
  color: white;
  fill: currentColor;
  background: #0066ce;
}

button.primary:hover {
  background-color: rgba(0, 102, 206, 0.58);
}

button.primary:active {
  color: #0066ce;
  fill: currentColor;
  background-color: white;
}

button.round {
  width: 64px;
  height: 64px;
  border-radius: 50%;
}

.buttonbar {
  margin-top: 1em;
  display: flex;
  flex-wrap: wrap;
  gap: 1em;
  justify-content: space-evenly;
}

#keyboard-container {
  display: block;
  position: relative;

  height: 600px;
  width: 1024px;
  background: palegreen;
  overflow: hidden;
  border: 5px solid red;
}

@media only screen and (max-width: 512px) {
  header {
    height: 100px;
  }

  header h1 {
    max-width: 320px;
    width: auto;
    font-size: 2rem;
  }

  .examples {
    width: 320px;
  }
}

@media (prefers-color-scheme: dark) {
  body {
    --surface: hsl(var(--hue, 212), 19%, 26%);
    --surface-border: hsl(0, 0%, 20%);
    --on-surface: hsl(0, 0%, 98%);
    --primary: hsl(var(--hue, 212), 100%, 50%);

    --secondary-surface: hsl(0, 0%, 19%, 0.3);
    --secondary-surface-border: hsl(0, 0%, 22%);
    --link: hsl(var(--hue, 212), 100%, 63%);

    --editable: #333;
    --editable-border: hsl(0, 0%, 13%);
    --on-editable: #fff;
  }
  h2,
  h3 {
    color: hsl(var(--hue, 212), 20%, 90%);
  }
}
