/* ========== Reset & Base ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
    --primary: #4361ee;
    --primary-light: #eef0ff;
    --secondary: #7209b7;
    --bg: #ffffff;
    --bg-card: #f8f9fa;
    --bg-card-hover: #f0f1f3;
    --text: #1a1a2e;
    --text-secondary: #6c757d;
    --text-light: #adb5bd;
    --border: #e9ecef;
    --shadow: 0 2px 8px rgba(0,0,0,0.08);
    --shadow-hover: 0 4px 16px rgba(0,0,0,0.12);
    --radius: 12px;
    --radius-sm: 8px;
    --easy: #22c55e;
    --medium: #f59e0b;
    --hard: #ef4444;
    --font: system-ui, -apple-system, "Segoe UI", "Microsoft YaHei", "PingFang SC", sans-serif;
    --max-width: 1200px;
    --header-h: 64px;
}
html { scroll-behavior: smooth; }
body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ========== Dark Mode ========== */
body.dark {
    --bg: #0f172a;
    --bg-card: #1e293b;
    --bg-card-hover: #334155;
    --text: #e2e8f0;
    --text-secondary: #94a3b8;
    --text-light: #64748b;
    --border: #334155;
    --shadow: 0 2px 8px rgba(0,0,0,0.3);
    --shadow-hover: 0 4px 16px rgba(0,0,0,0.4);
    --primary-light: #1e1b4b;
}

/* ========== Container ========== */
.container { max-width: var(--max-width); margin: 0 auto; padding: 0 20px; width: 100%; }

/* ========== Header ========== */
#header {
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    position: sticky; top: 0; z-index: 100;
    height: var(--header-h);
}
.header-inner {
    display: flex; align-items: center; gap: 16px; height: 100%;
}
.logo {
    display: flex; align-items: center; gap: 8px;
    font-size: 1.25rem; font-weight: 700; color: var(--text);
    white-space: nowrap; flex-shrink: 0;
}
.logo-img {
    height: 32px;
    width: 32px;
    object-fit: cover;
    border-radius: 8px;
    transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.logo:hover .logo-img {
    transform: scale(1.12) rotate(6deg);
}
.top-nav-link {
    padding: 6px 12px; border-radius: 18px; color: var(--text);
    font-size: 0.9rem; font-weight: 600; white-space: nowrap;
    border: 1px solid var(--border); background: var(--bg-card);
}
.top-nav-link:hover {
    text-decoration: none; color: var(--primary); border-color: var(--primary);
}
.search-box {
    flex: 1; display: flex; max-width: 480px; position: relative;
}
.search-box input {
    width: 100%; padding: 8px 16px; border: 2px solid var(--border);
    border-radius: 24px; font-size: 0.95rem; outline: none;
    background: var(--bg); color: var(--text);
    transition: border-color 0.2s;
}
.search-box input:focus { border-color: var(--primary); }
.search-btn {
    position: absolute; right: 4px; top: 4px; bottom: 4px;
    padding: 0 20px; background: var(--primary); color: #fff;
    border: none; border-radius: 20px; cursor: pointer;
    font-size: 0.9rem; font-weight: 500;
    transition: opacity 0.2s;
}
.search-btn:hover { opacity: 0.9; }
.theme-toggle {
    width: 40px; height: 40px; border-radius: 50%; border: 2px solid var(--border);
    background: var(--bg); cursor: pointer; display: flex; align-items: center;
    justify-content: center; flex-shrink: 0; color: #0f172a;
    transition: border-color 0.2s, background 0.2s, color 0.2s, box-shadow 0.2s;
}
.theme-toggle:hover { border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-light); }
.theme-icon {
    display: flex; align-items: center; justify-content: center;
    width: 22px; height: 22px;
}
.theme-icon svg {
    width: 100%; height: 100%; fill: none; stroke: currentColor;
    stroke-width: 2; stroke-linecap: round; stroke-linejoin: round;
}
.theme-icon-dark { display: none; }
body.dark .theme-icon-light { display: none; }
body.dark .theme-icon-dark { display: inline; }
body.dark .theme-toggle {
    background: #1e293b;
    border-color: #64748b;
    color: #f8fafc;
}
body.dark .theme-toggle:hover {
    border-color: #93c5fd;
    box-shadow: 0 0 0 3px rgba(147, 197, 253, 0.18);
}
.mobile-menu-btn {
    display: none; width: 40px; height: 40px; border: none;
    background: none; font-size: 1.5rem; cursor: pointer; color: var(--text);
}

/* ========== Main Content ========== */
#app { flex: 1; padding-top: 10px; padding-bottom: 40px; }

/* ========== Home Page ========== */
.home-hero { display: none; }

/* Category Grid */
.category-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 20px; margin-top: 24px;
}
.category-card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 24px; cursor: pointer;
    transition: all 0.2s; position: relative; overflow: hidden;
}
.category-card:hover {
    box-shadow: var(--shadow-hover); transform: translateY(-2px);
    text-decoration: none; background: var(--bg-card-hover);
}
.category-card-icon {
    width: 48px; height: 48px; border-radius: 12px;
    display: flex; align-items: center; justify-content: center;
    font-size: 1.5rem; margin-bottom: 12px;
}
.category-card h3 { font-size: 1.15rem; margin-bottom: 8px; }
.category-card p { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.5; }
.category-card .sub-tags {
    display: flex; flex-wrap: wrap; gap: 6px; margin-top: 12px;
}
.sub-tag {
    padding: 3px 10px; border-radius: 12px; font-size: 0.8rem;
    background: var(--primary-light); color: var(--primary);
}
.category-card .q-count {
    position: absolute; top: 16px; right: 16px;
    font-size: 0.8rem; color: var(--text-secondary);
}

/* Color themes for category cards */
.cat-programming .category-card-icon { background: #eef0ff; }
.cat-frontend .category-card-icon { background: #fef3c7; }
.cat-backend .category-card-icon { background: #dcfce7; }
.cat-cs .category-card-icon { background: #fce7f3; }
.cat-database .category-card-icon { background: #e0e7ff; }
.cat-devops .category-card-icon { background: #ccfbf1; }
.cat-bigdata .category-card-icon { background: #fef9c3; }
.cat-design .category-card-icon { background: #f3e8ff; }
.cat-ai .category-card-icon { background: #ffe4e6; }
.cat-soft .category-card-icon { background: #f0fdf4; }
.cat-open-source .category-card-icon { background: #e0f2fe; }

/* ========== Subcategory Page ========== */
.subcategory-header {
    padding: 24px 0;
}
.subcategory-header h2 { font-size: 1.6rem; margin-bottom: 8px; }
.subcategory-header p { color: var(--text-secondary); }
.subcategory-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 16px;
}
.subcategory-card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius-sm); padding: 20px; cursor: pointer;
    transition: all 0.2s; display: flex; align-items: center; gap: 16px;
}
.subcategory-card:hover {
    box-shadow: var(--shadow-hover); transform: translateY(-1px);
    text-decoration: none;
}
.subcategory-card .sc-name { font-weight: 600; font-size: 1rem; }
.subcategory-card .sc-count { font-size: 0.85rem; color: var(--text-secondary); }
.subcategory-card .sc-icon {
    width: 40px; height: 40px; border-radius: 10px;
    display: flex; align-items: center; justify-content: center;
    font-size: 1.2rem; background: var(--primary-light); flex-shrink: 0;
}

/* ========== Question List Page ========== */
.question-header { padding: 16px 0; }
.question-header h2 { font-size: 1.5rem; margin-bottom: 4px; }
.question-header p { color: var(--text-secondary); font-size: 0.95rem; }
.source-panel {
    margin-top: 12px; padding: 10px 12px;
    border: 1px solid var(--border); border-radius: 10px;
    background: var(--bg-card);
}
.source-panel-title {
    font-size: 0.82rem; color: var(--text-secondary);
    margin-bottom: 8px;
}
.source-panel-list {
    display: flex; flex-wrap: wrap; gap: 8px;
}
.source-link {
    display: inline-block; font-size: 0.82rem;
    padding: 4px 10px; border-radius: 14px;
    border: 1px solid var(--border);
    background: var(--bg);
}
.source-link:hover {
    text-decoration: none;
    border-color: var(--primary);
}
.question-actions {
    display: flex; gap: 12px; margin: 16px 0; flex-wrap: wrap;
}
.question-actions button {
    padding: 6px 16px; border-radius: 20px; border: 1px solid var(--border);
    background: var(--bg); color: var(--text); cursor: pointer; font-size: 0.85rem;
    transition: all 0.2s;
}
.question-actions button:hover { border-color: var(--primary); color: var(--primary); }
.difficulty-filter { display: flex; gap: 8px; align-items: center; margin-left: auto; }
.difficulty-filter button.active { background: var(--primary); color: #fff; border-color: var(--primary); }

.question-list { margin-top: 8px; }
.question-card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius-sm); margin-bottom: 12px;
    overflow: hidden; transition: box-shadow 0.2s;
}
.question-card:hover { box-shadow: var(--shadow); }
.question-title {
    padding: 16px 20px; cursor: pointer; display: flex; align-items: flex-start;
    gap: 12px; user-select: none;
}
.question-title:hover { background: var(--bg-card-hover); }
.question-number {
    flex-shrink: 0; width: 28px; height: 28px; border-radius: 50%;
    background: var(--primary-light); color: var(--primary);
    display: flex; align-items: center; justify-content: center;
    font-size: 0.85rem; font-weight: 600; margin-top: 2px;
}
.question-title h4 { flex: 1; font-size: 1rem; line-height: 1.5; }
.question-toggle {
    flex-shrink: 0; width: 24px; text-align: center;
    transition: transform 0.2s; color: var(--text-light);
    font-size: 0.8rem; margin-top: 4px;
}
.question-card.open .question-toggle { transform: rotate(180deg); }
.question-meta {
    display: flex; gap: 8px; align-items: center; margin-top: 8px; flex-wrap: wrap;
}
.difficulty-badge {
    padding: 2px 10px; border-radius: 10px; font-size: 0.75rem; font-weight: 600;
    color: #fff;
}
.difficulty-easy { background: var(--easy); }
.difficulty-medium { background: var(--medium); }
.difficulty-hard { background: var(--hard); }
.tag-badge {
    padding: 2px 8px; border-radius: 10px; font-size: 0.75rem;
    background: var(--primary-light); color: var(--primary);
}
.question-answer {
    max-height: 0; overflow: hidden; transition: max-height 0.3s ease;
}
.question-card.open .question-answer { max-height: none; }
.question-answer-inner {
    padding: 0 20px 20px 60px;
    border-top: 1px solid var(--border);
    padding-top: 16px;
    white-space: pre-wrap;
    line-height: 1.8;
    font-size: 0.95rem;
    color: var(--text);
}
.question-answer-inner strong { color: var(--primary); }
.question-source {
    margin-top: 12px; font-size: 0.8rem; color: var(--text-light);
    font-style: italic;
}

/* ========== Search Results ========== */
.search-header { padding: 16px 0; }
.search-header h2 { font-size: 1.3rem; }
.search-header h2 span { color: var(--primary); }
.search-result-card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius-sm); padding: 16px 20px;
    margin-bottom: 12px; cursor: pointer; transition: all 0.2s;
}
.search-result-card:hover { box-shadow: var(--shadow); }
.search-result-card .sr-category {
    font-size: 0.8rem; color: var(--text-secondary); margin-bottom: 6px;
}
.search-result-card h4 { font-size: 1rem; margin-bottom: 6px; }
.search-result-card .sr-preview {
    font-size: 0.9rem; color: var(--text-secondary);
    overflow: hidden; text-overflow: ellipsis;
    display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical;
}
.highlight { background: #fef08a; padding: 0 2px; border-radius: 2px; }
body.dark .highlight { background: #854d0e; color: #fef08a; }

/* ========== Open Source Catalog ========== */
.catalog-page { padding-top: 14px; }
.catalog-hero {
    display: flex; justify-content: space-between; align-items: flex-start;
    gap: 20px; padding: 20px 0 16px; border-bottom: 1px solid var(--border);
}
.catalog-kicker {
    font-size: 0.78rem; color: var(--primary); font-weight: 700;
    text-transform: uppercase; letter-spacing: 0;
}
.catalog-hero h2 { font-size: 1.65rem; margin: 4px 0 6px; }
.catalog-hero p { color: var(--text-secondary); max-width: 720px; font-size: 0.95rem; }
.catalog-update-panel {
    min-width: 210px; display: flex; flex-direction: column; align-items: flex-end; gap: 8px;
}
.catalog-update-btn {
    border: none; border-radius: 8px; padding: 9px 16px; background: var(--primary);
    color: #fff; cursor: pointer; font-weight: 700; white-space: nowrap;
}
.catalog-update-btn:hover { opacity: 0.92; }
.catalog-update-status {
    color: var(--text-secondary); font-size: 0.8rem; text-align: right; max-width: 300px;
}
.catalog-update-status.running { color: var(--medium); }
.catalog-update-status.completed { color: var(--easy); }
.catalog-update-status.failed { color: var(--hard); }
.catalog-stat-grid {
    display: grid; grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 12px; margin: 16px 0;
}
.catalog-stat {
    border: 1px solid var(--border); background: var(--bg-card);
    border-radius: 8px; padding: 14px 16px;
}
.catalog-stat span { display: block; font-size: 1.35rem; font-weight: 800; }
.catalog-stat small { color: var(--text-secondary); }
.catalog-filters {
    display: grid; grid-template-columns: 2fr repeat(6, minmax(120px, 1fr)) auto;
    gap: 10px; align-items: end; padding: 14px; border: 1px solid var(--border);
    border-radius: 8px; background: var(--bg-card);
}
.catalog-filters label {
    display: block; margin-bottom: 5px; color: var(--text-secondary);
    font-size: 0.78rem; font-weight: 700;
}
.catalog-filters input,
.catalog-filters select {
    width: 100%; height: 36px; border: 1px solid var(--border); border-radius: 8px;
    background: var(--bg); color: var(--text); padding: 0 10px; font-size: 0.88rem;
}
.catalog-filter-actions {
    display: flex; gap: 8px; align-items: center;
}
.catalog-filter-actions button,
.catalog-pager button {
    height: 36px; padding: 0 12px; border-radius: 8px; border: 1px solid var(--border);
    background: var(--primary); color: #fff; cursor: pointer; white-space: nowrap;
}
.catalog-filter-actions button.ghost,
.catalog-pager button {
    background: var(--bg); color: var(--text);
}
.catalog-pager button:disabled {
    opacity: 0.45; cursor: not-allowed;
}
.catalog-result-bar {
    display: flex; justify-content: space-between; align-items: center;
    gap: 12px; margin: 16px 0 12px; color: var(--text-secondary); font-size: 0.88rem;
}
.catalog-pager { display: flex; gap: 8px; }
.catalog-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(330px, 1fr));
    gap: 14px;
}
.catalog-card {
    border: 1px solid var(--border); border-radius: 8px; background: var(--bg-card);
    padding: 16px; min-height: 238px; display: flex; flex-direction: column; gap: 10px;
    transition: box-shadow 0.2s, transform 0.2s;
}
.catalog-card:hover { box-shadow: var(--shadow); transform: translateY(-1px); }
.catalog-card-top {
    display: flex; justify-content: space-between; align-items: center; gap: 8px;
}
.catalog-platform,
.catalog-score {
    display: inline-flex; align-items: center; height: 24px; border-radius: 12px;
    padding: 0 9px; font-size: 0.74rem; font-weight: 800;
}
.catalog-platform.github { background: #e0f2fe; color: #0369a1; }
.catalog-platform.huggingface { background: #fef3c7; color: #92400e; }
.catalog-score { background: var(--primary-light); color: var(--primary); }
.catalog-card h3 {
    font-size: 1rem; line-height: 1.35; overflow-wrap: anywhere;
}
.catalog-card p {
    color: var(--text-secondary); font-size: 0.88rem; line-height: 1.55;
    display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical;
    overflow: hidden;
}
.catalog-card-meta {
    display: flex; flex-wrap: wrap; gap: 7px; color: var(--text-secondary);
    font-size: 0.78rem; margin-top: auto;
}
.catalog-card-meta span {
    border: 1px solid var(--border); border-radius: 12px; padding: 2px 8px;
    background: var(--bg);
}
.catalog-chip-row { display: flex; flex-wrap: wrap; gap: 6px; }
.catalog-chip {
    padding: 3px 8px; border-radius: 10px; background: var(--primary-light);
    color: var(--primary); font-size: 0.74rem; line-height: 1.4;
}
.catalog-chip.muted {
    background: var(--bg); color: var(--text-secondary); border: 1px solid var(--border);
}
.catalog-chip.function {
    background: #dcfce7; color: #166534;
}
.catalog-chip.domain {
    background: #e0f2fe; color: #075985;
}
body.dark .catalog-platform.github { background: #0c4a6e; color: #bae6fd; }
body.dark .catalog-platform.huggingface { background: #78350f; color: #fde68a; }
body.dark .catalog-chip.function { background: #14532d; color: #bbf7d0; }
body.dark .catalog-chip.domain { background: #0c4a6e; color: #bae6fd; }

/* No Results */
.no-results { text-align: center; padding: 60px 0; color: var(--text-secondary); }
.no-results .nr-icon { font-size: 3rem; margin-bottom: 16px; }

/* ========== Footer ========== */
#footer {
    border-top: 1px solid var(--border); padding: 24px 0;
    background: var(--bg-card); margin-top: auto;
}
.footer-inner { text-align: center; }
.footer-inner p { font-size: 0.9rem; color: var(--text-secondary); }
.footer-stats { margin-top: 4px; font-size: 0.8rem; }

/* ========== Responsive ========== */
@media (max-width: 768px) {
    .header-inner { flex-wrap: wrap; height: auto; padding: 12px 16px; gap: 8px; }
    .search-box { order: 3; max-width: 100%; flex-basis: 100%; }
    .mobile-menu-btn { display: block; }
    .theme-toggle { width: 36px; height: 36px; font-size: 1rem; }
    .category-grid { grid-template-columns: 1fr; }
    .subcategory-grid { grid-template-columns: 1fr; }
    .catalog-hero { flex-direction: column; }
    .catalog-update-panel { align-items: flex-start; min-width: 0; }
    .catalog-update-status { text-align: left; }
    .catalog-stat-grid { grid-template-columns: repeat(2, 1fr); }
    .catalog-filters { grid-template-columns: 1fr; }
    .catalog-filter-actions { justify-content: stretch; }
    .catalog-filter-actions button { flex: 1; }
    .catalog-result-bar { flex-direction: column; align-items: flex-start; }
    .catalog-grid { grid-template-columns: 1fr; }
    .home-hero h1 { font-size: 1.6rem; }
    .home-stats { gap: 20px; }
    .question-answer-inner { padding-left: 20px; }
    #header { position: relative; }
    #breadcrumb { padding-top: 8px; }
}
@media (min-width: 769px) and (max-width: 1024px) {
    .category-grid { grid-template-columns: repeat(2, 1fr); }
    .subcategory-grid { grid-template-columns: repeat(2, 1fr); }
    .catalog-filters { grid-template-columns: repeat(3, 1fr); }
}