html,body { height:100%; margin:0; background:#f0f0f0; display:flex; align-items:center; justify-content:center; }
canvas { background: #ffffff; box-shadow: 0 6px 18px rgba(0,0,0,0.12); max-width:95vw; max-height:95vh; }
.controls { position:fixed; top:12px; right:12px; font-family:system-ui,Segoe UI,Roboto,Helvetica,Arial; }
button { padding:8px 12px; margin-left:6px; }