/* ========== AI 学习资源导航 — 样式 ========== */
:root {
  --bg: #f6f7fa;
  --bg-alt: #eef1f7;
  --card: #ffffff;
  --text: #17233b;
  --muted: #5c6b84;
  --border: #e3e8f0;
  --accent: #2563eb;
  --accent-dark: #1d4ed8;
  --accent-light: #e8effd;
  --green: #0e9f6e;
  --green-light: #e6f6f0;
  --amber: #b45309;
  --amber-light: #fdf1e2;
  --red: #d64545;
  --red-light: #fdecec;
  --shadow: 0 1px 3px rgba(23, 35, 59, 0.06), 0 4px 14px rgba(23, 35, 59, 0.05);
  --shadow-hover: 0 4px 8px rgba(23, 35, 59, 0.08), 0 10px 28px rgba(23, 35, 59, 0.10);
  --radius: 14px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-dark); }

img, svg { max-width: 100%; }

.container { max-width: 1120px; margin: 0 auto; padding: 0 20px; }
.container.narrow { max-width: 760px; }
.center { text-align: center; }

.muted { color: var(--muted); font-size: 0.9rem; }

/* ---------- 头部 ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; justify-content: space-between; height: 60px; gap: 12px; }
.logo { display: flex; align-items: center; gap: 9px; color: var(--text); font-weight: 700; font-size: 1.05rem; white-space: nowrap; }
.logo-mark {
  display: inline-flex; align-items: center; justify-content: center;
  width: 32px; height: 32px; border-radius: 9px;
  background: linear-gradient(135deg, var(--accent), #6d8dfc);
  color: #fff; font-size: 0.8rem; font-weight: 800; letter-spacing: 0.5px;
}
.site-nav { display: flex; gap: 4px; flex-wrap: wrap; }
.site-nav a {
  color: var(--muted); font-size: 0.95rem; padding: 7px 13px; border-radius: 9px;
  transition: color 0.15s, background 0.15s;
}
.site-nav a:hover { color: var(--text); background: var(--bg-alt); }
.site-nav a.active { color: var(--accent); background: var(--accent-light); font-weight: 600; }
.lang-switch {
  flex-shrink: 0;
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 6px 13px;
  border: 1px solid var(--accent-light);
  border-radius: 999px;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
}
.lang-switch:hover { background: var(--accent-light); }

/* ---------- 首页 Hero ---------- */
.hero {
  background: linear-gradient(180deg, #eaf0fe 0%, var(--bg) 100%);
  padding: 64px 0 48px;
  text-align: center;
}
.hero-kicker { color: var(--accent); font-weight: 600; font-size: 0.95rem; margin-bottom: 14px; }
.hero-title { font-size: clamp(1.9rem, 4.5vw, 3rem); line-height: 1.25; letter-spacing: 0.5px; margin-bottom: 16px; }
.hero-sub { color: var(--muted); max-width: 640px; margin: 0 auto 28px; font-size: 1.02rem; }
.hero-search { display: flex; gap: 10px; max-width: 620px; margin: 0 auto 36px; }
.hero-search input {
  flex: 1; min-width: 0; padding: 13px 18px; font-size: 1rem;
  border: 1px solid var(--border); border-radius: 12px; background: #fff;
  box-shadow: var(--shadow); outline: none; font-family: var(--font);
}
.hero-search input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15); }
.hero-search button {
  padding: 13px 26px; font-size: 1rem; font-weight: 600; color: #fff;
  background: var(--accent); border: none; border-radius: 12px; cursor: pointer;
  font-family: var(--font); transition: background 0.15s; white-space: nowrap;
}
.hero-search button:hover { background: var(--accent-dark); }
.hero-stats { display: flex; justify-content: center; gap: 14px; flex-wrap: wrap; }
.stat {
  background: #fff; border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 24px; min-width: 120px; box-shadow: var(--shadow);
}
.stat b { display: block; font-size: 1.5rem; color: var(--accent); }
.stat span { font-size: 0.85rem; color: var(--muted); }

/* ---------- 区块 ---------- */
.section { padding: 44px 0; }
.section-alt { background: var(--bg-alt); }
.section-head { display: flex; align-items: baseline; justify-content: space-between; margin-bottom: 22px; gap: 12px; flex-wrap: wrap; }
.section-head h2 { font-size: 1.4rem; }
.section-more { font-size: 0.92rem; font-weight: 500; }

/* ---------- 分类卡片 ---------- */
.cat-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; }
.cat-card {
  display: flex; flex-direction: column; gap: 6px;
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; color: var(--text); box-shadow: var(--shadow);
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}
.cat-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-hover); border-color: #cdd9ee; color: var(--text); }
.cat-icon { font-size: 1.6rem; }
.cat-name { font-weight: 700; font-size: 1.05rem; }
.cat-desc { color: var(--muted); font-size: 0.88rem; flex: 1; }
.cat-count { color: var(--accent); font-size: 0.85rem; font-weight: 600; }

/* ---------- 资源卡片 ---------- */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(310px, 1fr)); gap: 16px; }
.card {
  display: flex; flex-direction: column; gap: 9px;
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; box-shadow: var(--shadow);
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-hover); border-color: #cdd9ee; }
.card-badges { display: flex; flex-wrap: wrap; gap: 6px; }
.badge {
  display: inline-block; font-size: 0.75rem; font-weight: 600; line-height: 1;
  padding: 5px 9px; border-radius: 999px; white-space: nowrap;
}
.badge-type { background: var(--accent-light); color: var(--accent-dark); }
.badge-level { background: var(--bg-alt); color: var(--muted); }
.badge-star { background: #fff4d6; color: #92600a; }
.badge-pending { background: var(--amber-light); color: var(--amber); }
.badge-lang { background: var(--bg-alt); color: var(--muted); }
.cost-free { background: var(--green-light); color: var(--green); }
.cost-part { background: var(--amber-light); color: var(--amber); }
.cost-paid { background: var(--red-light); color: var(--red); }
.card-title { font-size: 1.05rem; line-height: 1.4; }
.card-title a { color: var(--text); }
.card-title a:hover { color: var(--accent); }
.card-org { color: var(--muted); font-size: 0.85rem; margin-top: -4px; }
.card-desc {
  color: #3c4c68; font-size: 0.9rem; flex: 1;
  display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden;
}
.card-foot { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; padding-top: 4px; border-top: 1px dashed var(--border); }
.card-more { margin-left: auto; font-size: 0.85rem; font-weight: 600; }

/* ---------- 工具栏 / 筛选 ---------- */
.breadcrumb { font-size: 0.85rem; color: var(--muted); padding: 20px 0 0; display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--accent); }
.crumb-sep { color: #b6c1d4; }
.page-head { padding: 14px 0 20px; }
.page-head h1 { font-size: clamp(1.5rem, 3vw, 2rem); }
.page-sub { color: var(--muted); margin-top: 8px; font-size: 0.98rem; }

.toolbar {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; margin-bottom: 24px; box-shadow: var(--shadow);
  display: flex; flex-direction: column; gap: 12px;
  position: sticky; top: 72px; z-index: 30;
}
.search-row { display: flex; gap: 10px; }
.search-row input {
  flex: 1; min-width: 0; padding: 11px 15px; font-size: 0.95rem; font-family: var(--font);
  border: 1px solid var(--border); border-radius: 10px; background: var(--bg); outline: none;
}
.search-row input:focus { border-color: var(--accent); background: #fff; box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12); }
.btn-ghost {
  padding: 10px 16px; font-size: 0.9rem; font-family: var(--font); cursor: pointer;
  border: 1px solid var(--border); border-radius: 10px; background: #fff; color: var(--muted);
}
.btn-ghost:hover { color: var(--text); border-color: #cdd9ee; }
.filter-row { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.chip-group { display: flex; gap: 8px; flex-wrap: wrap; }
.chip {
  padding: 7px 14px; font-size: 0.86rem; font-family: var(--font); cursor: pointer;
  border: 1px solid var(--border); border-radius: 999px; background: #fff; color: var(--muted);
  transition: all 0.15s; white-space: nowrap;
}
.chip:hover { border-color: var(--accent); color: var(--accent); }
.chip.active { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
.filter-row-sel { gap: 14px; }
.sel { font-size: 0.86rem; color: var(--muted); display: inline-flex; align-items: center; gap: 6px; }
.sel select {
  padding: 8px 10px; font-size: 0.88rem; font-family: var(--font);
  border: 1px solid var(--border); border-radius: 9px; background: #fff; color: var(--text); outline: none; cursor: pointer;
}
.result-count { margin-left: auto; font-size: 0.86rem; color: var(--muted); }
.empty { text-align: center; color: var(--muted); padding: 48px 0; font-size: 0.98rem; }

/* 分类导航条 */
.cat-nav { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 16px; }
.cat-nav a {
  font-size: 0.86rem; padding: 6px 13px; border-radius: 999px;
  background: var(--bg-alt); color: var(--muted);
}
.cat-nav a:hover { background: var(--accent-light); color: var(--accent); }
.cat-nav a.current { background: var(--accent); color: #fff; font-weight: 600; }

/* ---------- 详情页 ---------- */
.detail {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 32px; box-shadow: var(--shadow); margin-bottom: 12px;
}
.detail-title { font-size: clamp(1.4rem, 3vw, 1.9rem); line-height: 1.35; margin: 12px 0 6px; }
.detail-org { color: var(--muted); font-size: 1rem; margin-bottom: 20px; }
.detail-meta {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 10px 24px;
  background: var(--bg); border-radius: 12px; padding: 18px 20px; margin-bottom: 24px;
}
.meta-item { display: flex; flex-direction: column; gap: 2px; }
.meta-k { font-size: 0.78rem; color: var(--muted); }
.meta-v { font-size: 0.95rem; font-weight: 600; }
.detail-section h2 { font-size: 1.15rem; margin-bottom: 10px; }
.detail-section p { color: #3c4c68; }
.detail-tags { display: flex; flex-wrap: wrap; gap: 8px; margin: 22px 0; }
.tag { font-size: 0.8rem; color: var(--muted); background: var(--bg-alt); border-radius: 7px; padding: 4px 10px; }
.detail-cta { display: inline-block; }
.btn-primary {
  display: inline-block; background: var(--accent); color: #fff; font-weight: 600;
  padding: 12px 26px; border-radius: 11px; border: none; cursor: pointer; font-size: 0.98rem;
  font-family: var(--font); transition: background 0.15s;
}
.btn-primary:hover { background: var(--accent-dark); color: #fff; }
.detail-url { margin-top: 12px; word-break: break-all; font-size: 0.82rem; }
.related { padding-top: 8px; }

/* ---------- 学习路线 ---------- */
.path-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 16px; }
.path-card {
  display: flex; flex-direction: column; gap: 8px;
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 24px; color: var(--text); box-shadow: var(--shadow);
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}
.path-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-hover); border-color: #cdd9ee; color: var(--text); }
.path-card h3 { font-size: 1.2rem; }
.path-tagline { color: var(--accent); font-size: 0.92rem; font-weight: 500; }
.path-meta { color: var(--muted); font-size: 0.85rem; }
.path-goal { color: #3c4c68; font-size: 0.9rem; flex: 1; }
.path-cta { color: var(--accent); font-weight: 600; font-size: 0.9rem; }
.path-grid-lg { margin-top: 8px; }
.path-head h1 { margin-bottom: 6px; }
.path-facts { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; }
.path-intro { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px 28px; box-shadow: var(--shadow); margin-bottom: 28px; }

.steps { list-style: none; display: flex; flex-direction: column; gap: 16px; counter-reset: step; }
.step {
  display: flex; gap: 18px;
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 24px; box-shadow: var(--shadow);
}
.step-num {
  flex: none; width: 44px; height: 44px; border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), #6d8dfc); color: #fff;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.15rem; font-weight: 800;
}
.step-body { flex: 1; min-width: 0; }
.step-title { font-size: 1.08rem; margin-bottom: 6px; }
.step-desc { color: #3c4c68; font-size: 0.93rem; margin-bottom: 12px; }
.step-res-list { list-style: none; display: flex; flex-direction: column; gap: 7px; }
.step-res {
  display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap;
  background: var(--bg); border-radius: 9px; padding: 9px 13px; font-size: 0.9rem;
}
.step-res a { font-weight: 600; }
.step-res-meta { color: var(--muted); font-size: 0.8rem; display: inline-flex; align-items: center; gap: 6px; }
.step-tip { margin-top: 12px; font-size: 0.87rem; color: var(--amber); background: var(--amber-light); border-radius: 9px; padding: 9px 13px; }
.path-end { text-align: center; padding: 36px 0 8px; }

/* ---------- 关于页 ---------- */
.prose h2 { font-size: 1.2rem; margin: 28px 0 12px; }
.prose p, .prose li { color: #3c4c68; }
.prose ul, .prose ol { padding-left: 22px; display: flex; flex-direction: column; gap: 7px; margin: 10px 0; }
.prose code { background: var(--bg-alt); border-radius: 6px; padding: 2px 7px; font-size: 0.88em; font-family: Consolas, Monaco, monospace; }
.prose strong { color: var(--text); }

/* ---------- 404 ---------- */
.error-code { font-size: 4.5rem; color: var(--accent); letter-spacing: 2px; }

/* ---------- 页脚 ---------- */
.site-footer { border-top: 1px solid var(--border); background: #fff; margin-top: 48px; padding: 36px 0 44px; }
.footer-inner { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 24px; }
.footer-title { font-weight: 700; margin-bottom: 8px; font-size: 0.95rem; }
.footer-col p { font-size: 0.88rem; color: var(--muted); }

/* ---------- 移动端适配 ---------- */
@media (max-width: 860px) {
  .toolbar { position: static; }
  .grid { grid-template-columns: 1fr; }
  .cat-grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); }
  .detail { padding: 22px; }
  .step { flex-direction: column; gap: 12px; padding: 20px; }
}

@media (max-width: 560px) {
  .header-inner { height: auto; padding: 10px 0; flex-direction: column; align-items: flex-start; gap: 8px; }
  .site-nav { width: 100%; overflow-x: auto; padding-bottom: 2px; }
  .site-nav a { padding: 6px 10px; font-size: 0.9rem; }
  .hero { padding: 44px 0 36px; }
  .hero-search { flex-direction: column; }
  .hero-search button { width: 100%; }
  .hero-stats { gap: 10px; }
  .stat { min-width: calc(50% - 10px); padding: 12px 14px; }
  .search-row { flex-direction: column; }
  .result-count { margin-left: 0; width: 100%; }
  .filter-row-sel { flex-direction: column; align-items: stretch; }
  .sel { justify-content: space-between; }
  .sel select { flex: 1; }
  .detail-meta { grid-template-columns: 1fr 1fr; gap: 8px 14px; padding: 14px; }
  .card-more { margin-left: 0; width: 100%; text-align: right; }
  .footer-inner { grid-template-columns: 1fr; gap: 16px; }
  .error-code { font-size: 3.2rem; }
}

/* 减少动效偏好 */
@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; scroll-behavior: auto !important; }
}