/* スタイル */
* {
  margin: 0;
  padding: 0;
  overflow: hidden;
}
body {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  /* background: linear-gradient(-45deg,#9fcff8 0%, #9fcff8 50%, #b2cce2 50%, #b2cce2); */
  background: #b2cce2;
}
canvas {
  margin: 0 auto;
  display: block;
  border: 1px solid rgb(22, 130, 224);
  border-radius: 3px;
  box-shadow: 1px 1px 0 rgba(255,255,255,.3);
}