:root {
  color-scheme: light;
  --ink: #1c2430;
  --muted: #5c6778;
  --line: #e4e8ee;
  --accent: #1f6b4a;
  --accent-soft: #e8f4ee;
  --bg: #f6f7f9;
  --card: #ffffff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", "PingFang TC", "Microsoft JhengHei", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, #eef6f1 0, transparent 32rem),
    var(--bg);
}

main {
  max-width: 40rem;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3rem;
}

.badge {
  display: inline-block;
  margin: 0 0 0.85rem;
  padding: 0.25rem 0.7rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
}

h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.7rem, 5vw, 2.4rem);
  line-height: 1.25;
}

.lead, .meta {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.choices, .options {
  display: grid;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

a.choice, button.option, button.nav {
  font: inherit;
  text-align: left;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 0.9rem;
  padding: 0.95rem 1rem;
  cursor: pointer;
}

a.choice {
  display: block;
  text-decoration: none;
}

a.choice strong, button.option strong {
  display: block;
  margin-bottom: 0.15rem;
}

a.choice span, button.option span {
  color: var(--muted);
  font-size: 0.92rem;
}

a.choice:hover, button.option:hover, button.nav:hover {
  border-color: #b7d7c6;
}

button.option.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.stem {
  margin: 1.25rem 0 0;
  font-size: 1.25rem;
  line-height: 1.55;
}

.speeds {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  margin-top: 1.25rem;
}

.speeds span {
  color: var(--muted);
  font-size: 0.92rem;
  white-space: nowrap;
}

button.speed {
  font: inherit;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 999px;
  padding: 0.4rem 0.85rem;
  cursor: pointer;
  white-space: nowrap;
}

button.speed.selected {
  border-color: transparent;
  background: var(--accent);
  color: white;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 1.5rem;
}

button.nav {
  background: var(--accent);
  color: white;
  border-color: transparent;
}

button.nav.secondary {
  background: var(--card);
  color: var(--ink);
  border-color: var(--line);
}

button:disabled {
  opacity: 0.45;
  cursor: default;
}

.error {
  margin-top: 1rem;
  color: #8a2f2f;
}