:root {
    --brand: #4f46e5;
    --brand-600: #4f46e5;
    --brand-700: #4338ca;
    --brand-50: #eef2ff;
    --bg: #ffffff;
    --bg-soft: #f8fafc;
    --bg-hero: linear-gradient(135deg, #4f46e5 0%, #7c3aed 100%);
    --text: #1e293b;
    --text-soft: #64748b;
    --border: #e2e8f0;
    --radius: 14px;
    --shadow: 0 1px 3px rgba(15,23,42,.08), 0 1px 2px rgba(15,23,42,.04);
    --shadow-lg: 0 10px 25px rgba(15,23,42,.10);
}
html[data-theme="dark"] {
    --bg: #0b1120; --bg-soft: #111827; --text: #e2e8f0; --text-soft: #94a3b8;
    --border: #1e293b; --brand-50: #1e1b4b; --shadow: 0 1px 3px rgba(0,0,0,.4);
    --shadow-lg: 0 10px 25px rgba(0,0,0,.5);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
body {
    margin: 0; font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    color: var(--text); background: var(--bg); font-size: 15.5px; line-height: 1.65; -webkit-font-smoothing: antialiased;
}
a { color: var(--brand-600); text-decoration: none; }
a:hover { text-decoration: underline; }
code { font-family: 'JetBrains Mono', ui-monospace, monospace; font-size: .86em; background: var(--bg-soft); border: 1px solid var(--border); padding: 1px 6px; border-radius: 5px; }

/* ---------- Header ---------- */
.header {
    position: sticky; top: 0; z-index: 50; background: var(--bg); border-bottom: 1px solid var(--border);
}
.header-inner { max-width: 1080px; margin: 0 auto; display: flex; align-items: center; gap: 16px; padding: 14px 24px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--text); font-size: 15px; }
.brand .logo { display: grid; place-items: center; width: 30px; height: 30px; border-radius: 8px; background: var(--brand-600); color: #fff; }
.header .spacer { flex: 1; }
.header nav a { color: var(--text-soft); font-weight: 500; font-size: 14px; margin-left: 18px; }
.header nav a:hover { color: var(--text); text-decoration: none; }
.icon-btn { display: grid; place-items: center; width: 38px; height: 38px; border-radius: 9px; border: 1px solid var(--border); background: var(--bg-soft); color: var(--text); cursor: pointer; font-size: 16px; margin-left: 12px; }
.icon-btn:hover { background: var(--brand-50); }
.btn-support { margin-left: 18px; background: var(--brand-600); color: #fff !important; padding: 8px 16px; border-radius: 9px; font-size: 14px; font-weight: 600; }
.btn-support:hover { background: var(--brand-700); text-decoration: none; }

/* ---------- Hero ---------- */
.hero { background: var(--bg-hero); color: #fff; padding: 60px 24px 72px; text-align: center; }
.hero h1 { font-size: 2.4rem; font-weight: 800; margin: 0 0 10px; letter-spacing: -.02em; }
.hero p { font-size: 1.1rem; opacity: .92; margin: 0 auto 28px; max-width: 560px; }
.search-box { position: relative; max-width: 620px; margin: 0 auto; }
.search-box input {
    width: 100%; padding: 16px 18px 16px 48px; border-radius: 12px; border: none; font-size: 16px;
    box-shadow: var(--shadow-lg); color: var(--text); background: var(--bg);
}
.search-box input:focus { outline: 3px solid rgba(255,255,255,.4); }
.search-box .icon { position: absolute; left: 16px; top: 50%; transform: translateY(-50%); color: var(--text-soft); font-size: 18px; }
.search-results {
    position: absolute; top: 62px; left: 0; right: 0; background: var(--bg); border: 1px solid var(--border);
    border-radius: 12px; box-shadow: var(--shadow-lg); max-height: 56vh; overflow: auto; display: none; text-align: left; z-index: 60;
}
.search-results a { display: block; padding: 12px 18px; color: var(--text); border-bottom: 1px solid var(--border); }
.search-results a:hover { background: var(--bg-soft); text-decoration: none; }
.search-results a strong { display: block; font-size: 14.5px; }
.search-results a small { color: var(--text-soft); font-size: 12.5px; }
.search-results .cat { font-size: 11px; text-transform: uppercase; letter-spacing: .05em; color: var(--brand-600); font-weight: 700; }

/* ---------- Layout ---------- */
.container { max-width: 1080px; margin: 0 auto; padding: 0 24px; }
.section { padding: 48px 0; }
.section h2 { font-size: 1.5rem; font-weight: 700; margin: 0 0 6px; }
.section .sub { color: var(--text-soft); margin: 0 0 24px; }

/* Category grid */
.cat-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 18px; }
.cat-card { display: block; border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; background: var(--bg); transition: .15s; }
.cat-card:hover { border-color: var(--brand-600); box-shadow: var(--shadow-lg); transform: translateY(-2px); text-decoration: none; }
.cat-card .emoji { font-size: 30px; }
.cat-card h3 { margin: 12px 0 6px; font-size: 1.1rem; color: var(--text); }
.cat-card p { margin: 0 0 12px; font-size: 14px; color: var(--text-soft); }
.cat-card .count { font-size: 12.5px; color: var(--brand-600); font-weight: 600; }

/* Popular list */
.popular { display: grid; grid-template-columns: 1fr 1fr; gap: 10px 32px; }
.popular a { display: flex; align-items: center; gap: 10px; padding: 10px 0; color: var(--text); border-bottom: 1px solid var(--border); }
.popular a:hover { color: var(--brand-600); text-decoration: none; }
.popular a .arrow { margin-left: auto; color: var(--text-soft); }

/* ---------- Article page ---------- */
.breadcrumb { font-size: 13.5px; color: var(--text-soft); padding: 24px 0 0; }
.breadcrumb a { color: var(--text-soft); }
.article { display: grid; grid-template-columns: 1fr 240px; gap: 48px; padding: 24px 0 64px; align-items: start; }
.article-main { min-width: 0; }
.article h1 { font-size: 2rem; font-weight: 800; margin: 8px 0 20px; letter-spacing: -.01em; }
.article h2 { font-size: 1.35rem; font-weight: 700; margin: 36px 0 12px; scroll-margin-top: 80px; }
.article h3 { font-size: 1.1rem; font-weight: 700; margin: 24px 0 8px; }
.article p { margin: 0 0 14px; }
.article ul, .article ol { margin: 0 0 16px; padding-left: 22px; }
.article li { margin: 5px 0; }
.article img { max-width: 100%; border-radius: 10px; border: 1px solid var(--border); }

.steps { counter-reset: step; list-style: none; padding: 0; }
.steps > li { counter-increment: step; position: relative; padding: 0 0 18px 46px; }
.steps > li::before {
    content: counter(step); position: absolute; left: 0; top: 0; width: 30px; height: 30px;
    display: grid; place-items: center; border-radius: 50%; background: var(--brand-600); color: #fff; font-weight: 700; font-size: 14px;
}
.steps > li:not(:last-child)::after { content: ''; position: absolute; left: 14px; top: 34px; bottom: 4px; width: 2px; background: var(--border); }

.callout { border: 1px solid var(--border); border-left: 4px solid var(--brand-600); background: var(--bg-soft); border-radius: 10px; padding: 14px 18px; margin: 18px 0; font-size: 14.5px; }
.callout.tip { border-left-color: #10b981; }
.callout.warn { border-left-color: #f59e0b; }
.callout.info { border-left-color: #3b82f6; }
.callout strong { display: block; margin-bottom: 3px; }

table { width: 100%; border-collapse: collapse; margin: 18px 0; font-size: 14px; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--border); }
th { background: var(--bg-soft); font-size: 12px; text-transform: uppercase; letter-spacing: .04em; color: var(--text-soft); }

.badge { display: inline-block; padding: 2px 9px; border-radius: 999px; font-size: 12px; font-weight: 600; }
.badge-indigo { background: var(--brand-50); color: var(--brand-700); }
.badge-green { background: #dcfce7; color: #15803d; }
.badge-amber { background: #fef3c7; color: #b45309; }

/* Sidebar (in-article TOC + related) */
.article-side { position: sticky; top: 80px; }
.article-side h4 { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--text-soft); margin: 0 0 10px; }
.article-side a { display: block; padding: 5px 0; font-size: 13.5px; color: var(--text-soft); }
.article-side a:hover { color: var(--brand-600); text-decoration: none; }
.side-box { border: 1px solid var(--border); border-radius: 12px; padding: 16px; margin-bottom: 20px; }

/* Accordion (FAQ) */
.acc { border: 1px solid var(--border); border-radius: 12px; margin-bottom: 12px; overflow: hidden; background: var(--bg); }
.acc summary { cursor: pointer; padding: 16px 20px; font-weight: 600; list-style: none; display: flex; justify-content: space-between; align-items: center; }
.acc summary::-webkit-details-marker { display: none; }
.acc summary::after { content: '+'; color: var(--brand-600); font-size: 20px; }
.acc[open] summary::after { content: '−'; }
.acc .acc-body { padding: 0 20px 18px; color: var(--text-soft); font-size: 14.5px; }

/* Helpful widget */
.helpful { margin-top: 40px; padding: 24px; border: 1px solid var(--border); border-radius: 12px; text-align: center; }
.helpful button { margin: 8px 6px 0; padding: 8px 18px; border-radius: 9px; border: 1px solid var(--border); background: var(--bg); cursor: pointer; font-weight: 600; color: var(--text); }
.helpful button:hover { border-color: var(--brand-600); color: var(--brand-600); }

.page-nav { display: flex; justify-content: space-between; gap: 16px; margin-top: 40px; }
.page-nav a { flex: 1; border: 1px solid var(--border); border-radius: 10px; padding: 14px 18px; color: var(--text); }
.page-nav a:hover { border-color: var(--brand-600); text-decoration: none; }
.page-nav a small { display: block; color: var(--text-soft); font-size: 12px; }
.page-nav a.next { text-align: right; }

/* Footer */
.footer { border-top: 1px solid var(--border); background: var(--bg-soft); }
.footer-inner { max-width: 1080px; margin: 0 auto; padding: 40px 24px; display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 28px; }
.footer h5 { font-size: 13px; text-transform: uppercase; letter-spacing: .05em; color: var(--text-soft); margin: 0 0 12px; }
.footer a { display: block; color: var(--text); font-size: 14px; padding: 4px 0; }
.footer a:hover { color: var(--brand-600); text-decoration: none; }
.footer .muted { color: var(--text-soft); font-size: 13.5px; }
.footer-bottom { border-top: 1px solid var(--border); padding: 18px 24px; text-align: center; color: var(--text-soft); font-size: 13px; }

@media (max-width: 860px) {
    .article { grid-template-columns: 1fr; }
    .article-side { position: static; }
    .popular { grid-template-columns: 1fr; }
    .footer-inner { grid-template-columns: 1fr 1fr; }
    .header nav { display: none; }
}