style.css

:root {
  /* The 3 colors used on the page */
  --col-primary: rgb(57, 62, 65);
  --col-pop: rgb(233, 79, 55);
  --col-background: rgb(246, 247, 235);

  color: var(--col-primary);
  font-family: "Hind", system-ui, sans-serif;
  line-height: 1.5;
  font-weight: 400;
  font-style: normal;
  --pad: 1em;
  --pad-big: 1.7em;
}

/* Basic dark mode, with primary & background swapped */
@media (prefers-color-scheme: dark) {
  :root {
    --col-pop: rgb(233, 79, 55);
    --col-background: rgb(57, 62, 65);
    --col-primary: rgb(246, 247, 235);
  }
}

h1 {
  font-size: 2.1em;

  font-family: "Montserrat", system-ui, sans-serif;
  font-optical-sizing: auto;
  font-weight: 700;
  font-style: normal;

  padding-top: var(--pad);
  padding-bottom: var(--pad);
}

p {
  padding-bottom: var(--pad);
}

body {
  background-color: var(--col-background);
  margin: 0 auto;
}

/* In general, the width is at most 480px.
 * On mobile (< 480px) we limit the content to 450px
 * and set 15px of padding on either side.
 *
 * On bigger screens, no padding, but we limit the content to
 * 450px (as well) and scale up the canvas to 480px.
 * */
@media (width < 480px) {
  body {
    max-width: 450px;
    padding-left: 15px;
    padding-right: 15px;
  }

  canvas {
    width: 100%;
  }
}

@media (width > 480px) {
  body {
    max-width: 450px;
  }

  canvas {
    width: 480px;
    /* 15px = (480 - 450) / 2 */
    transform: translateX(-15px);
  }
}

#canvas-container {
  padding: var(--pad-big) 0;
}

canvas {
  --transition-duration: 0.6s;
  aspect-ratio: 1;
  accent-color: var(--col-pop);
  color: var(--col-primary);
  transition:
    color var(--transition-duration) cubic-bezier(0.3, 0.7, 0, 1),
    accent-color var(--transition-duration) cubic-bezier(0.3, 0.7, 0, 1);
}

footer {
  text-align: center;
  padding-top: var(--pad-big);
  padding-bottom: var(--pad-big);
  color: #6f7a80;
  font-size: 0.8em;
}

a:link,
a:visited {
  text-decoration: underline;
  color: #6f7a80;
}

a:hover {
  color: #393e41;
}

footer a:link,
footer a:visited {
  text-decoration: none;
  font-weight: bold;
}

footer a:hover {
  text-decoration: underline;
}