/* モバイルファーストのシンプルなスタイル */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", "Hiragino Kaku Gothic ProN", "Yu Gothic UI", sans-serif;
  background: #f8fafc;
  color: #1e293b;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.container {
  width: 100%;
  max-width: 480px;
  text-align: center;
}

h1 {
  font-size: 1.4rem;
  font-weight: 700;
  color: #1e40af;
  margin-bottom: 24px;
  line-height: 1.5;
}

.clock {
  font-size: 3.5rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: #0f172a;
  background: #ffffff;
  border-radius: 16px;
  padding: 24px 16px;
  box-shadow: 0 4px 12px rgba(30, 64, 175, 0.12);
  margin-bottom: 24px;
  letter-spacing: 0.05em;
}

.note {
  font-size: 0.85rem;
  color: #64748b;
  line-height: 1.7;
}

/* 画面が広い場合は少しだけ大きく */
@media (min-width: 600px) {
  h1 {
    font-size: 1.7rem;
  }
  .clock {
    font-size: 4.5rem;
  }
}