:root {
  color-scheme: dark;
  font-family: Inter, "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", system-ui, sans-serif;
  background: #02040a;
}

* { box-sizing: border-box; }

html, body { margin: 0; min-height: 100%; background: #02040a; }

body {
  min-height: 100vh;
  display: grid;
  place-items: center;
  overflow: hidden;
}

main {
  width: 100vw;
  height: 100vh;
  display: grid;
  place-items: center;
  padding: 10px;
}

canvas {
  width: min(calc(100vw - 20px), calc((100vh - 20px) * 16 / 9));
  height: min(calc(100vh - 20px), calc((100vw - 20px) * 9 / 16));
  background: #070911;
  border: 1px solid rgba(168, 85, 247, 0.45);
  border-radius: 16px;
  box-shadow: 0 0 60px rgba(124, 58, 237, 0.22);
  outline: none;
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
}

canvas:focus-visible { box-shadow: 0 0 0 3px #22d3ee, 0 0 60px rgba(124, 58, 237, 0.3); }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (prefers-reduced-motion: reduce) {
  canvas { scroll-behavior: auto; }
}