* { margin: 0; padding: 0; box-sizing: border-box; }
html, body {
  width: 100%;
  height: 100%;
  background: #211b2e;
  overflow: hidden;
  font-family: system-ui, "PingFang SC", sans-serif;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
}
canvas#cv {
  display: block;
  touch-action: none;
  max-width: 100%;
  max-height: 100%;
}