* { margin: 0; padding: 0; box-sizing: border-box; }
html, body {
  background: #05070f;
  overscroll-behavior: none;
  -webkit-user-select: none;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  touch-action: none;
}
#game {
  display: block;
  /* 16:9 letterbox：宽度和高度都按 16:9 约束，多余部分留黑边 */
  width: min(100vw, calc(100vh * 16 / 9));
  height: min(100vh, calc(100vw * 9 / 16));
  background: #05070f;
  touch-action: none;
}