:root {
  color-scheme: light dark;

  --bg-base: #f6f7fb;
  --bg-grad-1: rgba(99, 102, 241, 0.18);
  --bg-grad-2: rgba(16, 185, 129, 0.16);
  --bg-vignette-1: rgba(2, 6, 23, 0.02);
  --bg-vignette-2: rgba(2, 6, 23, 0.06);

  --text: #0f172a;
  --muted: rgba(15, 23, 42, 0.72);

  --card-bg: rgba(255, 255, 255, 0.78);
  --card-border: rgba(2, 6, 23, 0.1);
  --card-shadow: 0 14px 42px rgba(2, 6, 23, 0.14);

  --accent: #4f46e5;
  --accent-hover: #4338ca;
  --ring: rgba(79, 70, 229, 0.38);

  --secondary-bg: rgba(2, 6, 23, 0.06);
  --secondary-border: rgba(2, 6, 23, 0.12);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-base: #0b1220;
    --bg-grad-1: rgba(99, 102, 241, 0.14);
    --bg-grad-2: rgba(16, 185, 129, 0.12);
    --bg-vignette-1: rgba(255, 255, 255, 0.02);
    --bg-vignette-2: rgba(0, 0, 0, 0.55);

    --text: rgba(255, 255, 255, 0.92);
    --muted: rgba(255, 255, 255, 0.7);

    --card-bg: rgba(17, 24, 39, 0.72);
    --card-border: rgba(255, 255, 255, 0.12);
    --card-shadow: 0 18px 56px rgba(0, 0, 0, 0.55);

    --secondary-bg: rgba(255, 255, 255, 0.08);
    --secondary-border: rgba(255, 255, 255, 0.14);
  }
}

body {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px;
  color: var(--text);
  background-color: var(--bg-base);
  background-image: radial-gradient(1200px 600px at 20% 10%, var(--bg-grad-1), transparent),
    radial-gradient(900px 500px at 80% 30%, var(--bg-grad-2), transparent),
    linear-gradient(180deg, var(--bg-vignette-1), var(--bg-vignette-2));
}

.card {
  width: min(560px, 100%);
  padding: 28px;
  border-radius: 16px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  box-shadow: var(--card-shadow);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

@media (max-width: 420px) {
  .card {
    padding: 22px;
    border-radius: 14px;
  }
}

h1 {
  margin: 0 0 8px;
  letter-spacing: -0.02em;
  font-size: clamp(28px, 3.6vw, 40px);
  line-height: 1.15;
}

.subtitle {
  margin: 0 0 18px;
  color: var(--muted);
  line-height: 1.5;
}

.actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin: 10px 0 14px;
}

.actions button {
  flex: 1 1 160px;
}

button {
  appearance: none;
  border: 1px solid transparent;
  padding: 10px 14px;
  border-radius: 12px;
  cursor: pointer;
  font-weight: 650;
  letter-spacing: 0.005em;
  line-height: 1.2;
  color: white;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.14), rgba(255, 255, 255, 0)), var(--accent);
  box-shadow: 0 10px 22px rgba(2, 6, 23, 0.18);
  transition: transform 120ms ease, box-shadow 120ms ease, filter 120ms ease, background 120ms ease;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

@media (hover: hover) {
  button:hover {
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.16), rgba(255, 255, 255, 0)), var(--accent-hover);
    filter: brightness(1.02);
  }
}

button:active {
  transform: translateY(1px);
  box-shadow: 0 6px 14px rgba(2, 6, 23, 0.18);
}

button.secondary {
  color: var(--text);
  background: var(--secondary-bg);
  border: 1px solid var(--secondary-border);
  box-shadow: none;
}

@media (hover: hover) {
  button.secondary:hover {
    filter: brightness(1.03);
  }
}

button.secondary:active {
  transform: translateY(1px);
}

button:focus-visible {
  outline: 3px solid var(--ring);
  outline-offset: 2px;
}

.msg {
  min-height: 1.5em;
  margin: 0;
  opacity: 0.95;
}

.clock {
  min-height: 1.5em;
  margin: 6px 0 0;
  color: var(--muted);
}

.footer {
  margin-top: 18px;
  font-size: 14px;
  color: var(--muted);
}

.footer a {
  color: inherit;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

@media (hover: hover) {
  .footer a:hover {
    opacity: 0.9;
  }
}

.footer a:focus-visible {
  outline: 3px solid var(--ring);
  outline-offset: 3px;
  border-radius: 6px;
}