* {
  margin: 0;
  box-sizing: border-box;
  overflow: hidden;
}

body {
  background: #RRGGBBAA;<!-- 透明背景，原色#5530AB，robotcat.js:1070 -->
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
body canvas {
  border: none;
  outline: none;
}