html, body { margin: 0; height: 100%; background: #000; overflow: hidden; }
canvas { position: fixed; inset: 0; width: 100vw; height: 100vh; display: block; }
/* dunkler Rand, Blick zur Mitte */
.vignette { position: fixed; inset: 0; pointer-events: none;
  background: radial-gradient(ellipse at 50% 50%, transparent 35%, rgba(0,0,0,.55) 75%, rgba(0,0,0,.92) 100%); }
/* feine Monitor-Scanlines */
.scan { position: fixed; inset: 0; pointer-events: none; opacity: .18; mix-blend-mode: multiply;
  background: repeating-linear-gradient(to bottom, rgba(0,0,0,.9) 0 1px, transparent 1px 3px); }