*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  overflow: hidden;
  background: #000;
  font-family: system-ui, sans-serif;
}

canvas {
  display: block;
  width: 100vw;
  height: 100vh;
}

header {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 10;
  padding: 0.75rem 1rem;
  background: rgba(0, 0, 0, 0.5);
  border-radius: 0 0 0.5rem 0;
}

header a {
  color: rgba(255, 255, 255, 0.7);
  text-decoration: none;
  font-size: 0.875rem;
}

header a:hover {
  color: #fff;
}

#fallback {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 5;
  justify-content: center;
  align-items: center;
  background: rgba(0, 0, 0, 0.85);
  color: #fff;
  font-size: 1.25rem;
  text-align: center;
  padding: 2rem;
}

#fallback.visible {
  display: flex;
}