* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  background: #000;
  overflow: hidden;
}

#grid {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}