/* Minimal back button in top-left corner */
.back-btn {
  position: absolute;
  top: 16px;
  left: 16px;
  z-index: 10;
  text-decoration: none;
}
.back-btn svg {
  display: block;
  fill: none;
  stroke: #ffd700;
  transition: stroke 0.2s;
}
.back-btn:hover svg {
  stroke: #ffa500;
}

html,
body {
  margin: 0;
  padding: 0;
  display: grid;
  place-content: center center;
  height: 100vh;
  background: #0f0f23;
}

canvas {
  display: block;
  border: 3px solid #333;
  border-radius: 1em;
}