:root {
  --font: "SF Pro Text", "SF Pro Display", -apple-system, BlinkMacSystemFont,
    "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Noto Sans SC",
    "Microsoft YaHei", sans-serif;
  --radius: 14px;
  --shadow: 0 10px 40px rgba(15, 18, 24, 0.08);
  --max: 760px;
  --ease: 180ms ease;
}

:root[data-theme="light"] {
  --bg: #f4f1ea;
  --bg-elev: #fffcf6;
  --bg-header: rgba(244, 241, 234, 0.82);
  --text: #171717;
  --muted: #5d5a53;
  --border: #e4dfd4;
  --accent: #1d4ed8;
  --accent-soft: #dbe7ff;
  --chip: #ffffff;
  --toggle: #ece8de;
  --link: #1d4ed8;
}

:root[data-theme="dark"] {
  --bg: #0f1218;
  --bg-elev: #171c25;
  --bg-header: rgba(15, 18, 24, 0.78);
  --text: #f2f4f8;
  --muted: #a7b0bd;
  --border: #2a3140;
  --accent: #8bb4ff;
  --accent-soft: #1b2a4a;
  --chip: #1d2430;
  --toggle: #222a38;
  --link: #9ec0ff;
  --shadow: 0 12px 40px rgba(0, 0, 0, 0.35);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  background-image:
    radial-gradient(1200px 400px at 10% -10%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 55%),
    radial-gradient(900px 320px at 100% 0%, color-mix(in srgb, var(--accent) 10%, transparent), transparent 50%);
}

a { color: var(--link); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { opacity: 0.86; }

.skip {
  position: absolute;
  left: 12px;
  top: -40px;
  background: var(--bg-elev);
  padding: 8px 12px;
  border-radius: 8px;
  z-index: 20;
}
.skip:focus { top: 12px; }

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(16px);
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
}

.topbar-inner,
.wrap,
.footer-inner {
  width: min(var(--max), calc(100% - 32px));
  margin: 0 auto;
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: inherit;
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.logo {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  display: grid;
  place-items: center;
  background: var(--accent-soft);
  color: var(--accent);
}

.controls {
  display: flex;
  align-items: center;
  gap: 8px;
}

.seg, .icon-btn {
  border: 1px solid var(--border);
  background: var(--toggle);
  color: var(--text);
  border-radius: 999px;
  height: 36px;
}

.seg {
  display: flex;
  padding: 3px;
  gap: 2px;
}

.seg button, .icon-btn {
  appearance: none;
  cursor: pointer;
  font: inherit;
}

.seg button {
  border: 0;
  background: transparent;
  color: var(--muted);
  border-radius: 999px;
  padding: 0 12px;
  height: 28px;
}

.seg button[aria-pressed="true"] {
  background: var(--chip);
  color: var(--text);
  box-shadow: var(--shadow);
}

.icon-btn {
  width: 36px;
  display: grid;
  place-items: center;
}

.icon-btn svg { width: 18px; height: 18px; }
.icon-btn .sun { display: none; }
:root[data-theme="dark"] .icon-btn .moon { display: none; }
:root[data-theme="dark"] .icon-btn .sun { display: block; }

.hero, .doc {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.hero {
  margin: 36px auto 20px;
  padding: 36px 32px;
}

.doc {
  margin: 0 auto 48px;
  padding: 8px 32px 36px;
}

h1 {
  font-size: clamp(1.8rem, 4vw, 2.4rem);
  line-height: 1.2;
  letter-spacing: -0.04em;
  margin: 0 0 10px;
}

.lede, .muted, .meta, footer { color: var(--muted); }
.meta { font-size: 0.92rem; margin: 0; }

.pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 18px;
}

.pill {
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 0.85rem;
  font-weight: 600;
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 14px;
  margin-top: 24px;
}

.card {
  display: block;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--chip);
  color: inherit;
  text-decoration: none;
}

.card h2 {
  margin: 0 0 6px;
  font-size: 1.05rem;
}

.card p { margin: 0; color: var(--muted); font-size: 0.95rem; }

h2 {
  margin: 28px 0 8px;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
}

h3 { margin: 18px 0 6px; font-size: 1.02rem; }

p, li { color: var(--text); }
ul { padding-left: 1.2em; }
li + li { margin-top: 6px; }

.note {
  background: var(--accent-soft);
  border-radius: 12px;
  padding: 14px 16px;
  margin: 16px 0;
}

footer {
  border-top: 1px solid var(--border);
  padding: 24px 0 40px;
  font-size: 0.92rem;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

html[data-lang="en"] .lang-zh,
html[data-lang="zh"] .lang-en {
  display: none;
}

@media (max-width: 640px) {
  .hero, .doc { padding-left: 18px; padding-right: 18px; border-radius: 18px; }
  .brand span { display: none; }
}

@media print {
  .topbar, .controls, footer { display: none !important; }
  .hero, .doc { box-shadow: none; border: 0; }
}