/* 修改后的CSS */
body {
  margin: 0;
  overflow: hidden;
  background-color: #000;
}

canvas {
  display: block;
}

.serve-btn, .drop-btn {
    position: absolute;
    padding: 10px 20px;
    font-size: 16px;
    z-index: 1;
    cursor: pointer;
}

.serve-btn {
    top: 20px;
    left: 20px;
}

.drop-btn {
    top: 20px;
    left: 120px; /* 调整按钮位置 */
}