/* ============ 设计令牌 ============ */
:root {
  --primary: #2563EB;
  --primary-strong: #1D4ED8;
  --primary-soft: #DBEAFE;
  --accent: #F97316;
  --accent-soft: #FFEDD5;
  --purple: #7C3AED;
  --purple-soft: #EDE9FE;
  --bg: #F8FAFC;
  --surface: #FFFFFF;
  --surface-2: #F1F5F9;
  --border: #E2E8F0;
  --text: #1E293B;
  --text-2: #64748B;
  --text-3: #94A3B8;
  --shadow-sm: 0 1px 2px rgba(30, 41, 59, .06), 0 1px 3px rgba(30, 41, 59, .08);
  --shadow-md: 0 4px 10px rgba(30, 41, 59, .07), 0 2px 4px rgba(30, 41, 59, .05);
  --shadow-lg: 0 12px 28px rgba(30, 41, 59, .12), 0 4px 10px rgba(30, 41, 59, .07);
  --shadow-clay: 0 1px 1px rgba(30,41,59,.05), 0 4px 8px rgba(30,41,59,.06), 0 10px 20px rgba(30,41,59,.08);
  --radius-sm: 10px;
  --radius: 16px;
  --radius-lg: 22px;
  --font: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", "Helvetica Neue", Arial, sans-serif;
  --stage-小学: #F97316;
  --stage-小学-soft: #FFEDD5;
  --stage-初中: #2563EB;
  --stage-初中-soft: #DBEAFE;
  --stage-高中: #7C3AED;
  --stage-高中-soft: #EDE9FE;
  --stage-大学: #059669;
  --stage-大学-soft: #D1FAE5;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0F172A;
    --surface: #1E293B;
    --surface-2: #243349;
    --border: #334155;
    --text: #E2E8F0;
    --text-2: #94A3B8;
    --text-3: #64748B;
    --primary-soft: #1E3A8A;
    --accent-soft: #7C2D12;
    --purple-soft: #4C1D95;
    --stage-小学-soft: #7C2D12;
    --stage-初中-soft: #1E3A8A;
    --stage-高中-soft: #4C1D95;
    --stage-大学-soft: #064E3B;
    --shadow-sm: 0 1px 2px rgba(0,0,0,.3);
    --shadow-md: 0 4px 10px rgba(0,0,0,.35);
    --shadow-lg: 0 12px 28px rgba(0,0,0,.45);
    --shadow-clay: 0 1px 1px rgba(0,0,0,.25), 0 4px 8px rgba(0,0,0,.3), 0 10px 20px rgba(0,0,0,.35);
  }
}

/* ============ 基础 ============ */
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 15px;
}
a { color: var(--primary); text-decoration: none; }
img, svg { display: block; }
button { font-family: inherit; cursor: pointer; }
:focus-visible { outline: 3px solid var(--primary); outline-offset: 2px; border-radius: 6px; }
.skip-link {
  position: absolute; left: -9999px; top: 0; background: var(--primary); color: #fff;
  padding: 10px 16px; border-radius: 0 0 10px 0; z-index: 200;
}
.skip-link:focus { left: 0; }

/* ============ 顶栏 ============ */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: color-mix(in srgb, var(--surface) 86%, transparent);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  max-width: 1180px; margin: 0 auto; padding: 12px 24px;
  display: flex; align-items: center; gap: 28px;
}
.brand { display: flex; align-items: center; gap: 12px; color: var(--text); flex-shrink: 0; }
.brand-icon {
  width: 42px; height: 42px; border-radius: 13px; display: grid; place-items: center;
  color: #fff; background: linear-gradient(135deg, var(--primary), #60A5FA);
  box-shadow: var(--shadow-md);
}
.brand-icon svg { width: 22px; height: 22px; }
.brand-text { display: flex; flex-direction: column; line-height: 1.25; }
.brand-text strong { font-size: 16px; letter-spacing: .2px; }
.brand-text small { color: var(--text-2); font-size: 12px; }
.header-search { position: relative; flex: 1; max-width: 520px; margin-left: auto; }
.header-search .search-icon {
  position: absolute; left: 14px; top: 50%; transform: translateY(-50%);
  width: 18px; height: 18px; color: var(--text-3); pointer-events: none;
}
#search {
  width: 100%; padding: 11px 46px 11px 42px;
  border: 1.5px solid var(--border); border-radius: 999px;
  background: var(--surface-2); color: var(--text); font-size: 14.5px; font-family: inherit;
  transition: border-color .2s, background .2s, box-shadow .2s;
}
#search::placeholder { color: var(--text-3); }
#search:focus {
  outline: none; border-color: var(--primary); background: var(--surface);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--primary) 14%, transparent);
}
.search-kbd {
  position: absolute; right: 14px; top: 50%; transform: translateY(-50%);
  font-family: inherit; font-size: 12px; color: var(--text-3);
  background: var(--surface); border: 1px solid var(--border); border-radius: 6px;
  padding: 1px 8px; box-shadow: var(--shadow-sm);
}

/* ============ Hero ============ */
.hero {
  background:
    radial-gradient(52rem 20rem at 12% -4rem, color-mix(in srgb, var(--primary) 9%, transparent), transparent),
    radial-gradient(44rem 18rem at 92% 0rem, color-mix(in srgb, var(--accent) 8%, transparent), transparent),
    var(--bg);
  border-bottom: 1px solid var(--border);
}
.hero-inner {
  max-width: 1180px; margin: 0 auto; padding: 46px 24px 40px;
  display: grid; grid-template-columns: 1.25fr 1fr; gap: 36px; align-items: center;
}
.hero h1 {
  margin: 0 0 10px; font-size: clamp(26px, 3.4vw, 38px); line-height: 1.2; letter-spacing: .3px;
}
.hero-sub { margin: 0; color: var(--text-2); font-size: 15.5px; max-width: 46ch; }
.hero-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.stat-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 14px; text-align: center; box-shadow: var(--shadow-clay);
  transition: transform .2s, box-shadow .2s;
}
.stat-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); }
.stat-card svg { width: 20px; height: 20px; margin: 0 auto 6px; color: var(--primary); }
.stat-num { display: block; font-size: 22px; font-weight: 800; line-height: 1.2; font-variant-numeric: tabular-nums; }
.stat-label { font-size: 12.5px; color: var(--text-2); }

/* ============ 库区 ============ */
.library { max-width: 1180px; margin: 0 auto; padding: 26px 24px 60px; }
.stage-tabs { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 18px; }
.stage-tab {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 18px; border-radius: 999px; border: 1.5px solid var(--border);
  background: var(--surface); color: var(--text); font-size: 15px; font-weight: 600;
  transition: all .2s; box-shadow: var(--shadow-sm);
}
.stage-tab em {
  font-style: normal; font-size: 12px; font-weight: 700;
  background: var(--surface-2); color: var(--text-2);
  border-radius: 999px; padding: 1px 9px; font-variant-numeric: tabular-nums;
}
.stage-tab:hover { border-color: var(--primary); color: var(--primary); transform: translateY(-1px); }
.stage-tab.is-active {
  background: var(--primary); border-color: var(--primary); color: #fff; box-shadow: var(--shadow-md);
}
.stage-tab.is-active em { background: rgba(255,255,255,.22); color: #fff; }

/* 筛选栏 */
.filter-bar {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px; box-shadow: var(--shadow-sm); margin-bottom: 14px;
}
.filter-row { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.filter-label { font-size: 13px; color: var(--text-2); font-weight: 600; flex-shrink: 0; }
.select {
  appearance: none; -webkit-appearance: none;
  padding: 8px 34px 8px 13px; border: 1.5px solid var(--border); border-radius: 10px;
  background: var(--surface) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2364748B' stroke-width='2.4' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E") no-repeat right 11px center;
  color: var(--text); font-size: 14px; font-family: inherit; cursor: pointer;
  max-width: 220px; transition: border-color .2s;
}
.select:hover, .select:focus { border-color: var(--primary); outline: none; }
.chip-group { display: flex; gap: 8px; flex-wrap: wrap; }
.chip {
  padding: 7px 14px; border-radius: 999px; border: 1.5px solid var(--border);
  background: var(--surface-2); color: var(--text-2); font-size: 13px; font-weight: 600;
  transition: all .18s; min-height: 34px;
}
.chip:hover { border-color: var(--primary); color: var(--primary); }
.chip.is-active { background: var(--primary-soft); border-color: var(--primary); color: var(--primary); }
.sort-label { margin-left: auto; }

/* 结果栏 */
.result-bar {
  display: flex; align-items: center; gap: 14px; margin: 6px 2px 16px;
}
.result-count { color: var(--text-2); font-size: 13.5px; }
.result-count strong { color: var(--text); font-variant-numeric: tabular-nums; }
.clear-btn {
  border: none; background: none; color: var(--primary); font-size: 13px; font-weight: 600;
  padding: 6px 4px; border-radius: 8px;
}
.clear-btn:hover { text-decoration: underline; }

/* ============ 卡片网格 ============ */
.grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(248px, 1fr)); gap: 16px;
}
.book-card {
  position: relative; display: flex; flex-direction: column; gap: 12px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 18px; box-shadow: var(--shadow-clay); cursor: pointer; text-align: left;
  transition: transform .22s cubic-bezier(.2,.8,.3,1.1), box-shadow .22s, border-color .22s;
  animation: card-in .35s ease both;
}
@keyframes card-in {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}
.book-card:hover { transform: translateY(-5px); box-shadow: var(--shadow-lg); border-color: color-mix(in srgb, var(--primary) 35%, var(--border)); }
.book-card:hover .book-tile { transform: scale(1.05) rotate(-2deg); }
.book-card:active { transform: translateY(-2px) scale(.99); }
.book-top { display: flex; justify-content: space-between; align-items: center; gap: 8px; }
.badge {
  display: inline-flex; align-items: center; gap: 4px;
  font-size: 12px; font-weight: 700; border-radius: 999px; padding: 3px 11px;
  background: var(--surface-2); color: var(--text-2);
}
.badge-sm { font-size: 11px; padding: 2px 10px; }
.badge-小学 { background: var(--stage-小学-soft); color: var(--stage-小学); }
.badge-初中 { background: var(--stage-初中-soft); color: var(--stage-初中); }
.badge-高中 { background: var(--stage-高中-soft); color: var(--stage-高中); }
.badge-大学 { background: var(--stage-大学-soft); color: var(--stage-大学); }
.badge-term { background: var(--primary-soft); color: var(--primary); }
.badge-term--special { background: var(--accent-soft); color: var(--accent); }
.book-tile {
  width: 52px; height: 52px; border-radius: 15px; display: grid; place-items: center;
  background: linear-gradient(135deg, var(--primary), #60A5FA); color: #fff;
  box-shadow: var(--shadow-md); transition: transform .25s;
  flex-shrink: 0;
}
.book-tile svg { width: 26px; height: 26px; }
.book-card[data-stage="小学"] .book-tile { background: linear-gradient(135deg, #F97316, #FBBF24); }
.book-card[data-stage="初中"] .book-tile { background: linear-gradient(135deg, #2563EB, #60A5FA); }
.book-card[data-stage="高中"] .book-tile { background: linear-gradient(135deg, #7C3AED, #A78BFA); }
.book-body { flex: 1; min-height: 44px; }
.book-title {
  margin: 0 0 6px; font-size: 15.5px; font-weight: 700; line-height: 1.4;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.book-meta { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; font-size: 12.5px; color: var(--text-2); }
.book-meta .dot { width: 3px; height: 3px; border-radius: 50%; background: var(--text-3); }
.book-grade-big {
  position: absolute; right: 14px; bottom: 10px; font-size: 44px; font-weight: 900; line-height: 1;
  color: color-mix(in srgb, var(--surface-2) 60%, transparent);
  opacity: .5; pointer-events: none; font-variant-numeric: tabular-nums;
}
.book-foot { display: flex; align-items: center; justify-content: space-between; }
.book-size { font-size: 12px; color: var(--text-3); font-variant-numeric: tabular-nums; }
.book-open {
  display: inline-flex; align-items: center; gap: 5px; font-size: 13px; font-weight: 700;
  color: var(--primary); padding: 6px 2px; border-radius: 8px; transition: gap .18s;
}
.book-open svg { width: 15px; height: 15px; }
.book-card:hover .book-open { gap: 8px; }

/* 空状态 */
.empty {
  text-align: center; padding: 70px 20px; color: var(--text-2);
  border: 2px dashed var(--border); border-radius: var(--radius-lg); background: var(--surface);
}
.empty svg { width: 44px; height: 44px; margin: 0 auto 14px; color: var(--text-3); }
.empty h2 { margin: 0 0 6px; color: var(--text); font-size: 19px; }
.empty p { margin: 0 0 18px; font-size: 14px; }

/* ============ 按钮 ============ */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 20px; border-radius: 12px; font-size: 14px; font-weight: 700;
  border: 1.5px solid transparent; transition: all .2s; min-height: 44px;
}
.btn svg { width: 16px; height: 16px; }
.btn-primary { background: var(--primary); color: #fff; box-shadow: var(--shadow-md); }
.btn-primary:hover { background: var(--primary-strong); transform: translateY(-1px); }
.btn-ghost { background: var(--surface); color: var(--text); border-color: var(--border); }
.btn-ghost:hover { border-color: var(--primary); color: var(--primary); }
.icon-btn {
  width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center;
  border: none; background: var(--surface-2); color: var(--text-2); transition: all .18s;
}
.icon-btn:hover { background: var(--border); color: var(--text); }
.icon-btn svg { width: 18px; height: 18px; }

/* ============ 弹窗 ============ */
.modal { position: fixed; inset: 0; z-index: 300; display: grid; place-items: center; padding: 20px; }
[hidden] { display: none !important; }
.modal[hidden] { display: none; }
.modal-backdrop { position: absolute; inset: 0; background: rgba(15, 23, 42, .55); backdrop-filter: blur(4px); }
.modal-panel {
  position: relative; width: min(960px, 100%); max-height: 92vh;
  background: var(--surface); border-radius: var(--radius-lg); box-shadow: var(--shadow-lg);
  display: flex; flex-direction: column; overflow: hidden;
  animation: modal-in .28s cubic-bezier(.2,.9,.3,1.1);
}
@keyframes modal-in {
  from { opacity: 0; transform: translateY(18px) scale(.97); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
.modal-head {
  display: flex; align-items: flex-start; justify-content: space-between; gap: 12px;
  padding: 18px 20px 10px;
}
.modal-title-wrap { display: flex; flex-direction: column; gap: 5px; min-width: 0; }
.modal-title-wrap .badge { align-self: flex-start; }
.modal-title { margin: 0; font-size: 18px; line-height: 1.35; }
.modal-meta { padding: 0 20px; font-size: 13px; color: var(--text-2); display: flex; gap: 10px; flex-wrap: wrap; }
.modal-meta span { display: inline-flex; align-items: center; gap: 5px; }
.modal-meta svg { width: 13px; height: 13px; color: var(--text-3); }
.modal-actions { display: flex; gap: 10px; padding: 14px 20px; flex-wrap: wrap; }
.modal-viewer {
  position: relative; flex: 1; min-height: 320px; margin: 0 20px 12px;
  background: var(--surface-2); border-radius: var(--radius); border: 1px solid var(--border); overflow: hidden;
}
#viewer { width: 100%; height: 100%; min-height: 320px; border: none; display: block; background: #fff; }
.viewer-loading {
  position: absolute; inset: 0; display: flex; flex-direction: column; gap: 12px;
  align-items: center; justify-content: center; color: var(--text-2); font-size: 14px;
}
.viewer-loading[hidden] { display: none; }
.spinner {
  width: 30px; height: 30px; border-radius: 50%;
  border: 3px solid var(--border); border-top-color: var(--primary);
  animation: spin .8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
.modal-hint { margin: 0 20px 16px; font-size: 12px; color: var(--text-3); }

/* ============ 页脚 ============ */
.site-footer {
  border-top: 1px solid var(--border); background: var(--surface);
  padding: 26px 24px; text-align: center; color: var(--text-2); font-size: 13px;
}
.footer-inner { max-width: 1180px; margin: 0 auto; }
.footer-meta { color: var(--text-3); font-size: 12px; margin: 4px 0 0; }

/* ============ 响应式 ============ */
@media (max-width: 900px) {
  .hero-inner { grid-template-columns: 1fr; gap: 22px; }
  .sort-label { margin-left: 0; }
}
@media (max-width: 640px) {
  .header-inner { flex-wrap: wrap; gap: 12px; padding: 10px 16px; }
  .header-search { order: 3; max-width: none; width: 100%; }
  .hero-inner { padding: 30px 16px 26px; }
  .hero-stats { gap: 10px; }
  .stat-num { font-size: 19px; }
  .library { padding: 20px 16px 50px; }
  .grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 12px; }
  .book-card { padding: 14px; }
  .modal { padding: 10px; }
  .modal-panel { max-height: 96vh; }
  .modal-viewer { margin: 0 12px 10px; }
  .modal-actions { padding: 10px 12px; }
  .modal-head { padding: 14px 12px 8px; }
  .modal-meta { padding: 0 12px; }
  .modal-hint { margin: 0 12px 12px; }
  .filter-row { gap: 10px; }
  .select { max-width: none; flex: 1; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
  .book-card:hover { transform: none; }
}