body {
  margin: 0;
  padding: 0;
  background: #111;
  color: white;
  font-family: "微软雅黑", sans-serif;
  text-align: center;
}

.container {
  padding: 20px;
}

canvas {
  margin-top: 20px;
  background: #222;
  border-radius: 50%;
  box-shadow: 0 0 10px #000;
  width: 400px;
  height: 400px;
}

button, .buttons a {
  background: #fff;
  color: #000;
  border: none;
  padding: 10px 20px;
  margin: 10px;
  font-weight: bold;
  cursor: pointer;
  border-radius: 5px;
  text-decoration: none;
}

button:hover, .buttons a:hover {
  background: #444;
  color: #fff;
}


.pointer-bottom {
  width: 0;
  height: 0;
  border-left: 12px solid transparent;
  border-right: 12px solid transparent;
  border-bottom: 20px solid yellow;
  position: absolute;
  bottom: 0px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
}