*{margin:0;padding:0;box‑sizing:border‑box}
body{overflow:hidden;background:#1a1a1a}
canvas{display:block}
.tip{
  position:absolute;
  top:12px;
  left:12px;
  color:#fff;
  background:rgba(0,0,0,0.55);
  padding:8px 14px;
  border‑radius:8px;
  font‑size:14px;
  z‑index:99;
}