html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background-color: #111;  /* 背景黑色 */
  display: flex;
  justify-content: center;
  align-items: center;

  -webkit-user-select: none;
  user-select: none;
  -webkit-touch-callout: none;
  -webkit-user-drag: none;
  touch-action: none;
}

canvas {
  display: block;
  border-radius: 12px;
  box-shadow: 0 0 20px rgba(255, 255, 255, 0.1);

  /* ✅ 補強防複製/長按行為 */
  -webkit-user-select: none;
  user-select: none;
  -webkit-touch-callout: none;
  -webkit-user-drag: none;
}