html, body {
  height: 100%;
  margin: 0;
  background: #000;
  overflow: hidden;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans JP", sans-serif;
}

#c {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  display: block;
}

#hud {
  position: fixed;
  inset: 0;
  display: grid;
  place-content: center;
  text-align: center;
  pointer-events: none;
  user-select: none;
  padding: 24px;
}

#time {
  font-size: clamp(42px, 8vw, 96px);
  letter-spacing: 0.04em;
  color: rgba(255,255,255,0.92);
  text-shadow: 0 0 18px rgba(255,255,255,0.18);
}

#date {
  margin-top: 10px;
  font-size: clamp(14px, 2.2vw, 20px);
  color: rgba(255,255,255,0.70);
  text-shadow: 0 0 14px rgba(255,255,255,0.14);
}

.hidden {
  opacity: 0;
}