* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
  width: 100%;
  height: 100%;
  background: #000;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

#gameCanvas {
  display: block;
  /* 保持 4:3 比例自适应，最大不超出视口 */
  max-width: 100vw;
  max-height: 100vh;
  /* 让 Canvas 在小屏幕上等比缩放 */
  object-fit: contain;
  cursor: crosshair;
}