:root {
  --bg: #f5f7fb;
  --surface: #ffffff;
  --text: #1b2430;
  --muted: #5e6b7a;
  --line: #dce3ec;
  --brand: #2563eb;
  --brand-strong: #1d4ed8;
  --on-brand: #ffffff;
  --chip-bg: #e8f0ff;
  --kbd-bg: #f1f3f5;
  --kbd-border: #c4c9d0;
  --radius: 14px;
}

body[data-theme="dark"] {
  --bg: #0f172a;
  --surface: #111b2e;
  --text: #e5ecf7;
  --muted: #a9b7cc;
  --line: #22334f;
  --brand: #60a5fa;
  --brand-strong: #3b82f6;
  --on-brand: #0b1220;
  --chip-bg: #1b2b47;
  --kbd-bg: #1e293b;
  --kbd-border: #334155;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.65;
  scroll-behavior: smooth;
}

a {
  color: inherit;
}

/* ── Layout ──────────────────────────── */

.container {
  width: min(1100px, 92vw);
  margin: 0 auto;
}

/* ── Topbar ──────────────────────────── */

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(6px);
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: 60px;
}

.brand {
  font-weight: 700;
  font-size: 18px;
  text-decoration: none;
  white-space: nowrap;
}

.topbar-controls {
  display: flex;
  gap: 8px;
}

.control-group {
  display: inline-flex;
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
}

.control-btn {
  border: 0;
  background: var(--surface);
  color: var(--text);
  padding: 6px 10px;
  min-width: 44px;
  font-size: 13px;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.control-btn + .control-btn {
  border-left: 1px solid var(--line);
}

.control-btn.active {
  background: var(--brand);
  color: var(--on-brand);
}

.control-btn:not(.active):hover {
  background: var(--chip-bg);
}

/* ── Table of Contents ────────────────── */

.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.toc a {
  text-decoration: none;
  font-size: 14px;
  color: var(--muted);
  padding: 6px 10px;
  border-radius: 999px;
  transition: color 0.15s, background 0.15s;
}

.toc a.active,
.toc a:hover {
  color: var(--brand-strong);
  background: var(--chip-bg);
}

/* ── Page ─────────────────────────────── */

.page {
  padding: 30px 0 52px;
}

/* ── Hero ─────────────────────────────── */

.hero {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 32px 28px;
  margin-bottom: 18px;
}

.hero h1 {
  margin: 8px 0 14px;
  font-size: clamp(28px, 4vw, 38px);
  line-height: 1.2;
}

.hero p {
  max-width: 680px;
  color: var(--muted);
  font-size: 16px;
}

.badge {
  display: inline-block;
  margin: 0;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--chip-bg);
  color: var(--brand-strong);
  font-size: 13px;
  font-weight: 600;
}

.hero-actions {
  display: flex;
  gap: 10px;
  margin-top: 18px;
}

.button {
  display: inline-block;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
  border-radius: 10px;
  text-decoration: none;
  padding: 8px 16px;
  font-size: 14px;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}

.button.primary {
  background: var(--brand);
  border-color: var(--brand);
  color: var(--on-brand);
}

.button.primary:hover {
  background: var(--brand-strong);
  border-color: var(--brand-strong);
}

.button:not(.primary):hover {
  background: var(--chip-bg);
}

/* ── Cards ────────────────────────────── */

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px 28px;
  margin-bottom: 16px;
}

.card h2 {
  margin-top: 0;
  font-size: 22px;
}

.card h3 {
  margin: 24px 0 10px;
  font-size: 17px;
}

.card h3:first-of-type {
  margin-top: 4px;
}

.card h4 {
  margin: 0 0 6px;
  font-size: 15px;
}

/* ── Step Grid ────────────────────────── */

.step-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 12px;
  margin-bottom: 20px;
}

.step-grid article {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 16px;
  transition: border-color 0.15s;
}

.step-grid article:hover {
  border-color: var(--brand);
}

/* ── Keyboard Shortcut ────────────────── */

kbd {
  display: inline-block;
  padding: 2px 7px;
  font-size: 13px;
  font-family: "Fira Code", "Cascadia Code", Consolas, monospace;
  color: var(--text);
  background: var(--kbd-bg);
  border: 1px solid var(--kbd-border);
  border-radius: 5px;
  white-space: nowrap;
}

/* ── Tables ───────────────────────────── */

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 12px;
  overflow: hidden;
  border-radius: 10px;
}

th,
td {
  border: 1px solid var(--line);
  text-align: left;
  padding: 10px 14px;
  font-size: 14px;
}

th {
  background: var(--chip-bg);
  font-weight: 600;
}

tbody tr:hover {
  background: color-mix(in srgb, var(--chip-bg) 40%, transparent);
}

/* ── Code ─────────────────────────────── */

code {
  padding: 2px 6px;
  font-size: 13px;
  font-family: "Fira Code", "Cascadia Code", Consolas, monospace;
  background: var(--chip-bg);
  border-radius: 4px;
  color: var(--brand-strong);
}

/* ── Tip / Muted ──────────────────────── */

.tip {
  margin-top: 14px;
  color: var(--muted);
  font-size: 14px;
  border-left: 3px solid var(--brand);
  padding-left: 12px;
}

/* ── Demo Video ────────────────────────── */

.video-wrapper {
  position: relative;
  width: 100%;
  border-radius: 10px;
  overflow: hidden;
  border: 1px solid var(--line);
  margin-top: 14px;
}

.demo-video {
  display: block;
  width: 100%;
  max-height: 540px;
  background: #000;
  border-radius: 10px;
}

/* ── FAQ Details ──────────────────────── */

details {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 12px 16px;
  margin-top: 10px;
  transition: border-color 0.15s;
}

details[open] {
  border-color: var(--brand);
}

summary {
  font-weight: 600;
  cursor: pointer;
  padding: 2px 0;
}

details p {
  margin: 10px 0 4px;
  color: var(--muted);
  font-size: 14px;
}

/* ── Lists ────────────────────────────── */

ul, ol {
  padding-left: 20px;
}

li {
  margin-bottom: 6px;
}

/* ── Footer ───────────────────────────── */

.footer {
  border-top: 1px solid var(--line);
  padding: 22px 0;
  color: var(--muted);
  font-size: 14px;
  text-align: center;
}

/* ── Responsive ───────────────────────── */

@media (max-width: 760px) {
  .topbar-inner {
    flex-direction: column;
    align-items: flex-start;
    padding: 8px 0;
  }

  .topbar-controls {
    width: 100%;
  }

  .hero {
    padding: 20px;
  }

  .card {
    padding: 18px;
  }

  .hero-actions {
    flex-wrap: wrap;
  }

  .step-grid {
    grid-template-columns: 1fr;
  }
}