html, body {
  margin: 0;
  padding: 0;
  background: #000;
  overflow: hidden;
}
#c {
  display: block;
  width: 100vw;
  height: 100vh;
}
#gate {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #000;
  color: #b6ff5a;
  font: 600 20px ui-monospace, Menlo, Consolas, monospace;
  letter-spacing: 0.12em;
  cursor: pointer;
  z-index: 10000;
  transition: opacity 0.8s ease;
}
#gate.hide {
  opacity: 0;
  pointer-events: none;
}