style.css

:root {
  --yellow: #fcfa81;
  --brown: #42331c;
}

*,
*:after,
*:before {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
body, h1, h2, h3, h4, h5, h6, p, ul {
  margin: 0;
}

h1 {
  margin-top: 10px;
  color: var(--brown);
}

body {
  background-color: #eee;
  font-family: 'Roboto', Arial, Helvetica, sans-serif;
  color: #888;
  text-align: center;
}

.container {
  width: 300px;
  height: 300px;
  margin: 1.2em auto;
  background-color: var(--yellow);
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  border-radius: 4px;
  box-shadow: 0 2px 3px 4px rgba(0,0,0,0.1);
}

canvas {
  display: block;
  margin: 0 auto;
  background-color: var(--yellow);
}

#loading {
  display: none;
}

#error {
  display: none;
  color: #ff4949;
  padding: 1em;
}

button {
  display: block;
  margin: 0 auto;
  margin-bottom: 3em;
  padding: 0.5em 2em;
}

footer {
  width: 300px;
  margin: 0 auto;
}

p {
  font-size: 0.8rem;
  text-align: center;
}

a {
  color: #333;
  text-decoration: none;
}

a:hover {
  color: var(--brown);
}

.git {
  margin-top: 0.3em;
  text-align: center;
}