body {
  font-family: sans-serif;
  text-align: center;
  background: #fffbe6;
  margin: 0;
  padding: 20px;
}



/* 基础卡片样式 */
.card {
  position: absolute;
  width: 60px;
  height: 60px;
  border-radius: 6px;
  cursor: pointer;
  object-fit: contain;
  border: 4px solid #e0e0e0; /* 浅灰描边 */
  transition: transform 0.2s, opacity 0.2s; /* 添加透明度变化 */
}

/* 可点击（顶层）卡片 */
.card.top    { opacity:1; filter:brightness(1.1); cursor:pointer; }
.card.covered{ opacity:.45; filter:grayscale(100%) brightness(.7); cursor:not-allowed; }

/* 第一层随机稀疏布局，留空隙 */
#game-board{
  position:relative;
  width:430px;
  height:430px;
  margin:0 auto;
}

.card:hover {
  transform: scale(1.1);
}

.slot-card {
  width: 60px;
  height: 60px;
  background: #eee;
  border: 5px solid #e0e0e0;
  border-radius: 6px;
  font-size: 28px;
  line-height: 60px;
}
#game-over {
  margin-top: 20px;
  font-size: 20px;
}