html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  overflow: hidden;
  background-color: #000;
  -webkit-tap-highlight-color: transparent;
}

#gameCanvas {
  display: block;
  margin: 0 auto; /* 水平居中 */
  background-color: #222;
}

#retryBtn {
  position: fixed;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 1.5rem;
  padding: 10px 20px;
  border: none;
  border-radius: 8px;
  background-color: #ffcc00;
  color: #000;
  cursor: pointer;
  display: none;
  user-select: none;
  box-shadow: 0 4px 8px rgba(0,0,0,0.3);
  transition: background-color 0.3s ease;
}

#retryBtn:hover {
  background-color: #e6b800;
}