/* =====================================================
   Home (front-page) styles
   Five anchors (problem-driven narrative):
     #problem / #compare / #method / #case / #about
   ===================================================== */

/* 锚点偏移，避免被 sticky header 遮挡 */
.home-section { scroll-margin-top: calc(var(--header-h) + 24px); }

/* ===== Anchor nav (sticky) ===== */
.home-nav {
    position: sticky;
    top: var(--header-h);
    z-index: 40;
    background: rgba(248,250,252,.92);
    backdrop-filter: saturate(180%) blur(12px);
    -webkit-backdrop-filter: saturate(180%) blur(12px);
    border-bottom: 1px solid var(--color-border);
}
.home-nav ul {
    max-width: var(--container);
    margin: 0 auto;
    padding: 0 var(--space-5);
    list-style: none;
    display: flex;
    gap: var(--space-6);
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: var(--fs-sm);
}
.home-nav li { flex-shrink: 0; }
.home-nav a {
    display: block;
    padding: var(--space-3) 0;
    color: var(--color-ink-soft);
    text-decoration: none;
    border-bottom: 2px solid transparent;
    transition: color .16s ease, border-color .16s ease;
}
.home-nav a:hover { color: var(--color-primary); }
.home-nav a.is-active {
    color: var(--color-primary);
    border-bottom-color: var(--color-accent);
}

/* ===== Section base ===== */
.home-section {
    padding: var(--space-20) 0;
    border-bottom: 1px solid var(--color-border);
}
.home-section:last-of-type { border-bottom: 0; }

/* 交替背景：problem(白) → compare(浅) → method(白) → case(浅) → about(白) */
.home-section--compare,
.home-section--case { background: var(--color-bg-soft); }

.section-head { margin-bottom: var(--space-10); max-width: 68ch; }
.section-head__eyebrow {
    font-family: var(--font-mono);
    font-size: var(--fs-xs);
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin: 0 0 var(--space-3);
}
.section-head__title {
    font-size: var(--fs-3xl);
    margin: 0;
    color: var(--color-ink);
}

.section-cta {
    margin-top: var(--space-10);
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-3);
}

/* ===== Problem ===== */
.home-section--problem .tag-row { margin-top: var(--space-8); }

/* ===== Compare: SEO vs GEO 对比表 ===== */
.prose--compare { max-width: 100%; }
.prose--compare table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-6) 0;
    font-size: var(--fs-base);
}
.prose--compare thead th {
    text-align: left;
    padding: var(--space-3) var(--space-4);
    background: var(--color-primary);
    color: #fff;
    font-family: var(--font-mono);
    font-size: var(--fs-sm);
    letter-spacing: 0.3px;
    border: 0;
}
.prose--compare tbody td {
    padding: var(--space-3) var(--space-4);
    border-top: 1px solid var(--color-border);
    vertical-align: top;
}
.prose--compare tbody tr:nth-child(odd) td { background: #fff; }
.prose--compare tbody td:first-child {
    font-weight: 600;
    color: var(--color-primary);
    width: 20%;
}

/* ===== Method: observation sub-section ===== */
.section-subhead {
    margin: var(--space-12) 0 var(--space-5);
    font-family: var(--font-mono);
    font-size: var(--fs-sm);
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
}
.card-grid--obs .card { border-left: 3px solid var(--color-accent); border-radius: var(--radius-md); }

/* ===== About ===== */
.home-section--about .prose { max-width: 72ch; }

/* ===== Case cards ===== */
.card-grid--case .card { background: var(--color-primary); color: #fff; border: 0; }
.card-grid--case .card:hover { background: var(--color-primary-600); }
.card-grid--case .card__link { color: #fff; }
.card-grid--case .card__title { color: #fff; }
.card-grid--case .card__eyebrow { color: var(--color-accent-500); }
.card-grid--case .card__metric { color: var(--color-accent-500); }
.card-grid--case .card__meta { color: rgba(255,255,255,.65); }

/* ===== Coop: service grid ===== */
.service-grid {
    list-style: none;
    padding: 0;
    margin: var(--space-10) 0 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--space-5);
}
.service-card {
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    transition: border-color .16s ease, transform .08s ease;
}
.service-card:hover { border-color: var(--color-accent); transform: translateY(-2px); }
.service-card h3 { margin: 0 0 var(--space-3); font-size: var(--fs-lg); color: var(--color-primary); }
.service-card p { margin: 0 0 var(--space-4); font-size: var(--fs-sm); color: var(--color-ink-muted); }
.service-card .card-link {
    font-family: var(--font-mono);
    font-size: var(--fs-xs);
    color: var(--color-accent);
    text-decoration: none;
    letter-spacing: 0.3px;
}
.service-card .card-link:hover { text-decoration: underline; }

@media (max-width: 640px) {
    .home-section { padding: var(--space-12) 0; }
    .section-head__title { font-size: var(--fs-2xl); }
}