:root {
  --bg1: #0a1433;
  --bg2: #060c1f;
  --fg: #ffffff;
  --muted: rgba(255, 255, 255, 0.55);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(circle at top, var(--bg1), var(--bg2));
  color: var(--fg);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
               Roboto, Oxygen, Ubuntu, Cantarell, "Helvetica Neue", Arial, sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

#fullscreenBtn {
  position: fixed;
  top: 16px;
  right: 16px;
  width: 36px;
  height: 36px;
  background: none;
  border: none;
  color: var(--fg);
  font-size: 20px;
  opacity: 0.4;
  cursor: pointer;
}

#fullscreenBtn:hover { opacity: 0.9; }

.title {
  font-size: 1.6rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  margin-bottom: 36px;
}

.clock {
  display: flex;
  align-items: baseline;
}

#time {
  font-size: 14vw;
  line-height: 1;
  font-weight: 500;
}

#period {
  font-size: 3.5vw;
  margin-left: 12px;
  opacity: 0.75;
}

.centre {
  margin-top: 32px;
  font-size: 1.15rem;
  letter-spacing: 0.15em;
  color: var(--muted);
}