/* ===== RESET ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
    --physics:    #3b82f6;
    --chemistry:  #10b981;
    --biology:    #22c55e;
    --electronics:#8b5cf6;
    --robotics:   #f59e0b;
    --diy:        #ef4444;
    --dark:       #0f172a;
    --dark2:      #1e293b;
    --accent:     #6366f1;
    --text:       #334155;
    --muted:      #64748b;
    --bg:         #f8fafc;
    --white:      #ffffff;
    --border:     #e2e8f0;
    --radius:     12px;
    --shadow:     0 1px 4px rgba(0,0,0,0.07), 0 4px 16px rgba(0,0,0,0.05);
    --shadow-lg:  0 8px 32px rgba(0,0,0,0.12);
}
html { scroll-behavior: smooth; }
body { font-family: 'Segoe UI', system-ui, sans-serif; color: var(--text); background: var(--bg); line-height: 1.7; }
.container { max-width: 1140px; margin: 0 auto; padding: 0 20px; }
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }

/* ===== HEADER ===== */
.site-header { background: var(--dark); color: #fff; position: sticky; top: 0; z-index: 100; box-shadow: 0 2px 16px rgba(0,0,0,0.4); }
.site-header .container { display: flex; align-items: center; justify-content: space-between; height: 58px; gap: 16px; }
.header-top { display: flex; align-items: center; gap: 10px; }
.sister-link { color: rgba(255,255,255,0.55); font-size: 0.82rem; transition: color 0.2s; white-space: nowrap; }
.sister-link:hover { color: rgba(255,255,255,0.9); }
.header-divider { color: rgba(255,255,255,0.2); }
.site-brand { display: flex; align-items: center; gap: 8px; color: #fff; font-size: 1rem; white-space: nowrap; }
.brand-icon { font-size: 1.3rem; }
.brand-name { font-weight: 400; }
.brand-name strong { font-weight: 700; }

/* Nav */
.nav-toggle-input { display: none; }
.nav-toggle-label { display: none; flex-direction: column; gap: 5px; cursor: pointer; padding: 8px; }
.nav-toggle-label span { display: block; width: 22px; height: 2px; background: #fff; border-radius: 2px; transition: all 0.3s; }
.site-nav ul { list-style: none; display: flex; gap: 2px; margin: 0; padding: 0; }
.site-nav ul li a { color: rgba(255,255,255,0.75); padding: 6px 12px; border-radius: 20px; font-size: 0.85rem; font-weight: 500; transition: all 0.2s; display: block; white-space: nowrap; }
.site-nav ul li a:hover { background: rgba(255,255,255,0.1); color: #fff; }

/* ===== HERO ===== */
.hero { background: linear-gradient(135deg, var(--dark) 0%, #1e293b 60%, #0f3460 100%); color: #fff; padding: 52px 0 48px; }
.hero-text { text-align: center; margin-bottom: 40px; }
.hero-text h1 { font-size: clamp(1.8rem, 3.5vw, 2.6rem); margin-bottom: 10px; }
.hero-text p { color: rgba(255,255,255,0.7); font-size: 1.05rem; margin-bottom: 20px; }
.hero-link { display: inline-block; background: rgba(255,255,255,0.12); border: 1px solid rgba(255,255,255,0.25); color: #fff; padding: 9px 22px; border-radius: 24px; font-size: 0.9rem; font-weight: 600; transition: all 0.2s; }
.hero-link:hover { background: rgba(255,255,255,0.22); }

/* Cat grid */
.cat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 12px; max-width: 960px; margin: 0 auto; }
.cat-card { background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.1); border-radius: var(--radius); padding: 22px 14px; text-align: center; color: #fff; transition: all 0.25s; cursor: pointer; }
.cat-card:hover { transform: translateY(-4px); background: rgba(255,255,255,0.13); }
.cat-card span { font-size: 2rem; display: block; margin-bottom: 10px; }
.cat-card h3 { font-size: 0.92rem; font-weight: 700; margin-bottom: 4px; }
.cat-card small { font-size: 0.78rem; color: rgba(255,255,255,0.6); }
.cat-card.physics    { border-color: rgba(59,130,246,0.4); }
.cat-card.chemistry  { border-color: rgba(16,185,129,0.4); }
.cat-card.biology    { border-color: rgba(34,197,94,0.4); }
.cat-card.electronics{ border-color: rgba(139,92,246,0.4); }
.cat-card.robotics   { border-color: rgba(245,158,11,0.4); }
.cat-card.diy        { border-color: rgba(239,68,68,0.4); }
.cat-card.physics:hover    { border-color: var(--physics); }
.cat-card.chemistry:hover  { border-color: var(--chemistry); }
.cat-card.biology:hover    { border-color: var(--biology); }
.cat-card.electronics:hover{ border-color: var(--electronics); }
.cat-card.robotics:hover   { border-color: var(--robotics); }
.cat-card.diy:hover        { border-color: var(--diy); }

/* ===== POSTS SECTION ===== */
.posts-section { padding: 52px 0; }
.section-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 28px; }
.section-head h2 { font-size: 1.5rem; color: var(--dark); }
.post-total { background: var(--border); color: var(--muted); padding: 3px 12px; border-radius: 20px; font-size: 0.82rem; }

/* ===== POSTS GRID ===== */
.posts-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }

/* ===== POST CARD ===== */
.post-card { background: var(--white); border-radius: var(--radius); box-shadow: var(--shadow); border: 1px solid var(--border); overflow: hidden; transition: transform 0.22s, box-shadow 0.22s; }
.post-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); }
.card-img-wrap { display: block; position: relative; height: 200px; overflow: hidden; }
.card-img-wrap img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.3s; }
.post-card:hover .card-img-wrap img { transform: scale(1.04); }
.card-cat-badge { position: absolute; top: 10px; left: 10px; padding: 3px 10px; border-radius: 20px; font-size: 0.75rem; font-weight: 700; color: #fff; background: var(--dark2); display: flex; align-items: center; gap: 5px; }
.card-cat-badge.tag-physics     { background: var(--physics); }
.card-cat-badge.tag-chemistry   { background: var(--chemistry); }
.card-cat-badge.tag-biology     { background: var(--biology); }
.card-cat-badge.tag-electronics { background: var(--electronics); }
.card-cat-badge.tag-robotics    { background: var(--robotics); }
.card-cat-badge.tag-diy         { background: var(--diy); }
.card-body { padding: 18px 20px; }
.card-title { font-size: 1.05rem; font-weight: 700; line-height: 1.4; margin-bottom: 8px; }
.card-title a:hover { color: var(--accent); }
.card-excerpt { color: var(--muted); font-size: 0.88rem; line-height: 1.6; margin-bottom: 14px; }
.card-footer { display: flex; justify-content: space-between; align-items: center; border-top: 1px solid var(--border); padding-top: 12px; }
.card-date { color: var(--muted); font-size: 0.8rem; }
.card-link { color: var(--accent); font-size: 0.85rem; font-weight: 600; transition: gap 0.2s; }
.card-link:hover { text-decoration: underline; }

/* ===== TAG PILLS ===== */
.tag-pill { display: inline-block; padding: 3px 11px; border-radius: 20px; font-size: 0.78rem; font-weight: 600; color: #fff; margin-right: 4px; margin-bottom: 4px; }
.tag-physics     { background: var(--physics); }
.tag-chemistry   { background: var(--chemistry); }
.tag-biology     { background: var(--biology); }
.tag-electronics { background: var(--electronics); }
.tag-robotics    { background: var(--robotics); }
.tag-diy         { background: var(--diy); }

/* ===== TAG PAGE ===== */
.tag-page {}
.tag-header { padding: 52px 0 44px; text-align: center; color: #fff; background: var(--dark2); }
.tag-header.tag-physics     { background: linear-gradient(135deg, #1e3a8a, var(--physics)); }
.tag-header.tag-chemistry   { background: linear-gradient(135deg, #064e3b, var(--chemistry)); }
.tag-header.tag-biology     { background: linear-gradient(135deg, #14532d, var(--biology)); }
.tag-header.tag-electronics { background: linear-gradient(135deg, #4c1d95, var(--electronics)); }
.tag-header.tag-robotics    { background: linear-gradient(135deg, #78350f, var(--robotics)); }
.tag-header.tag-diy         { background: linear-gradient(135deg, #7f1d1d, var(--diy)); }
.tag-icon { font-size: 3rem; margin-bottom: 12px; }
.tag-header h1 { font-size: 2rem; margin-bottom: 10px; }
.tag-header p { color: rgba(255,255,255,0.75); max-width: 480px; margin: 0 auto 16px; }
.count-badge { background: rgba(255,255,255,0.18); padding: 4px 14px; border-radius: 20px; font-size: 0.83rem; }

/* ===== POST FULL ===== */
.post-header { background: var(--dark); color: #fff; padding: 52px 0 44px; }
.post-tags { margin-bottom: 16px; }
.post-title { font-size: clamp(1.5rem, 3vw, 2.2rem); line-height: 1.25; margin-bottom: 16px; }
.post-lead { font-size: 1.05rem; color: rgba(255,255,255,0.72); max-width: 640px; border-left: 3px solid rgba(255,255,255,0.3); padding-left: 16px; margin-top: 14px; line-height: 1.65; }
.post-meta { display: flex; gap: 20px; color: rgba(255,255,255,0.6); font-size: 0.88rem; margin-top: 14px; }
.post-hero-image { background: var(--dark2); }
.post-hero-image img { max-height: 460px; object-fit: cover; margin: 0 auto; border-radius: 0 0 var(--radius) var(--radius); }
.post-body { padding: 44px 0; }

/* Post layout with sidebar */
.post-layout { display: grid; grid-template-columns: 1fr 280px; gap: 40px; align-items: start; }

/* Post content typography */
.post-content h2 { font-size: 1.45rem; margin: 36px 0 14px; color: var(--dark); border-bottom: 2px solid var(--border); padding-bottom: 8px; }
.post-content h3 { font-size: 1.2rem; margin: 26px 0 10px; color: var(--dark2); }
.post-content p { margin-bottom: 16px; }
.post-content img { border-radius: var(--radius); margin: 20px 0; box-shadow: var(--shadow); }
.post-content ul, .post-content ol { padding-left: 22px; margin-bottom: 16px; }
.post-content li { margin-bottom: 6px; }
.post-content table { width: 100%; border-collapse: collapse; margin: 20px 0; font-size: 0.93rem; }
.post-content th { background: var(--dark2); color: #fff; padding: 10px 14px; text-align: left; }
.post-content td { padding: 9px 14px; border-bottom: 1px solid var(--border); }
.post-content tr:hover td { background: #f1f5f9; }
.post-content blockquote { border-left: 4px solid var(--accent); background: #f0f4ff; padding: 14px 18px; border-radius: 0 8px 8px 0; margin: 20px 0; color: var(--dark2); }
.post-content code { background: #f1f5f9; padding: 2px 6px; border-radius: 4px; font-family: 'Consolas', monospace; font-size: 0.87em; color: #dc2626; }
.post-content pre { background: var(--dark); padding: 18px; border-radius: 8px; overflow-x: auto; margin: 20px 0; }
.post-content pre code { background: none; color: #e2e8f0; padding: 0; }

/* Ghost card classes */
.kg-width-wide { margin-left: calc(50% - 50vw + 20px); margin-right: calc(50% - 50vw + 20px); max-width: 1100px; }
.kg-width-full { margin-left: calc(50% - 50vw); margin-right: calc(50% - 50vw); width: 100vw; }
.kg-image-card img { border-radius: 8px; }
.kg-embed-card { display: flex; justify-content: center; }
.kg-callout-card { display: flex; gap: 12px; padding: 16px 18px; border-radius: 8px; margin: 20px 0; }
.kg-callout-card-green { background: #ecfdf5; border: 1px solid #a7f3d0; }
.kg-callout-card-yellow { background: #fffbeb; border: 1px solid #fde68a; }
.kg-callout-card-red { background: #fff1f2; border: 1px solid #fecdd3; }
.kg-callout-card-blue { background: #eff6ff; border: 1px solid #bfdbfe; }
.kg-callout-emoji { font-size: 1.3rem; flex-shrink: 0; }

/* Sidebar */
.post-sidebar { display: flex; flex-direction: column; gap: 16px; }
.sidebar-card { background: var(--white); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow); }
.sidebar-card h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 10px; color: var(--dark); }
.sidebar-card p { font-size: 0.88rem; color: var(--muted); line-height: 1.6; margin-bottom: 14px; }
.sim-link { border-top: 3px solid var(--accent); }
.safety-card { border-top: 3px solid var(--diy); }
.safety-card h4 { color: #b45309; }
.safety-card p { margin: 0; color: #92400e; }
.sidebar-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.btn-sim { display: block; text-align: center; background: var(--accent); color: #fff; padding: 10px 16px; border-radius: 8px; font-size: 0.9rem; font-weight: 600; transition: background 0.2s; }
.btn-sim:hover { background: #4f46e5; }

/* Post footer */
.post-footer { padding: 24px 0 44px; border-top: 1px solid var(--border); }
.post-share { display: flex; align-items: center; gap: 12px; }
.post-share span { color: var(--muted); font-size: 0.88rem; }
.share-fb { background: #1877f2; color: #fff; padding: 7px 18px; border-radius: 20px; font-size: 0.85rem; font-weight: 600; transition: opacity 0.2s; }
.share-fb:hover { opacity: 0.85; }

/* ===== BUTTONS ===== */
.btn { display: inline-block; padding: 10px 22px; border-radius: 8px; background: var(--accent); color: #fff; font-weight: 600; font-size: 0.9rem; cursor: pointer; border: none; transition: all 0.2s; }
.btn:hover { background: #4f46e5; transform: translateY(-1px); }
.btn-outline { background: transparent; border: 2px solid var(--border); color: var(--text); }
.btn-outline:hover { border-color: var(--accent); color: var(--accent); background: transparent; transform: none; }

/* ===== PAGINATION ===== */
.pagination { display: flex; justify-content: center; align-items: center; gap: 16px; margin-top: 44px; }
.pagination span { color: var(--muted); font-size: 0.9rem; }

/* ===== ERROR ===== */
.error-page { padding: 80px 0; text-align: center; }
.error-icon { font-size: 3.5rem; margin-bottom: 12px; }
.error-page h1 { font-size: 3.5rem; color: var(--dark); margin-bottom: 10px; }
.error-page p { color: var(--muted); font-size: 1.05rem; margin-bottom: 24px; }

/* ===== FOOTER ===== */
.site-footer { background: var(--dark); color: rgba(255,255,255,0.7); padding: 44px 0 24px; }
.footer-grid { display: grid; grid-template-columns: 1.5fr 1fr 1fr; gap: 32px; margin-bottom: 32px; }
.footer-brand .brand-icon { font-size: 1.5rem; margin-bottom: 6px; display: block; }
.footer-brand strong { color: #fff; font-size: 1rem; display: block; margin-bottom: 8px; }
.footer-brand p { font-size: 0.85rem; line-height: 1.6; color: rgba(255,255,255,0.5); }
.footer-nav-group h4, .footer-sister h4 { color: rgba(255,255,255,0.5); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 14px; }
.footer-nav-group ul { list-style: none; }
.footer-nav-group ul li { margin-bottom: 8px; }
.footer-nav-group ul li a { color: rgba(255,255,255,0.65); font-size: 0.88rem; transition: color 0.2s; }
.footer-nav-group ul li a:hover { color: #fff; }
.sister-card { display: flex; align-items: center; gap: 12px; background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.1); border-radius: 10px; padding: 14px; transition: all 0.2s; color: #fff; }
.sister-card:hover { background: rgba(255,255,255,0.12); }
.sister-card span { font-size: 1.6rem; }
.sister-card strong { display: block; font-size: 0.9rem; }
.sister-card span:last-child, .sister-card div > span { font-size: 0.78rem; color: rgba(255,255,255,0.55); }
.footer-bottom { border-top: 1px solid rgba(255,255,255,0.1); padding-top: 20px; text-align: center; font-size: 0.82rem; color: rgba(255,255,255,0.35); }
.footer-bottom a { color: rgba(255,255,255,0.5); transition: color 0.2s; }
.footer-bottom a:hover { color: #fff; }

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
    .post-layout { grid-template-columns: 1fr; }
    .post-sidebar { flex-direction: row; flex-wrap: wrap; }
    .sidebar-card { flex: 1; min-width: 220px; }
    .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 768px) {
    .nav-toggle-label { display: flex; }
    .site-nav { display: none; position: absolute; top: 58px; left: 0; right: 0; background: var(--dark2); padding: 12px 16px; box-shadow: 0 8px 24px rgba(0,0,0,0.3); }
    .nav-toggle-input:checked ~ .site-nav { display: block; }
    .site-nav ul { flex-direction: column; gap: 2px; }
    .site-header .container { position: relative; flex-wrap: nowrap; }
    .cat-grid { grid-template-columns: repeat(3, 1fr); }
    .posts-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 24px; }
}
@media (max-width: 480px) {
    .cat-grid { grid-template-columns: repeat(2, 1fr); }
    .header-top { gap: 6px; }
    .sister-link, .header-divider { display: none; }
}