/* ═══════════════════════════════════════════
   4sh.education — Bengali Site Stylesheet
   ═══════════════════════════════════════════ */

/* ── Reset & Base ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
    --saffron:     #FF6700;
    --saffron-dk:  #E05500;
    --charcoal:    #1E1E1E;
    --body-text:   #2D2D2D;
    --muted:       #666666;
    --bg:          #FFFFFF;
    --bg-alt:      #F9F7F4;
    --bg-dark:     #1A1A1A;
    --header-h:    72px;
    --max-w:       1200px;
    --section-py:  100px;
    --font-sans:   'Helvetica Neue', Helvetica, Arial, sans-serif;
    --font-serif:  Georgia, 'Times New Roman', serif;
    --font-bengali:'Hind Siliguri', 'Noto Sans Bengali', 'Vrinda', sans-serif;
    --transition:  0.3s ease;
}

html { scroll-behavior: smooth; font-size: 20px; }

body {
    font-family: var(--font-bengali);
    color: var(--body-text);
    background: var(--bg);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
}

img { display: block; max-width: 100%; height: auto; }
a   { text-decoration: none; color: inherit; }

/* ═══════════════════════════════════════════
   HEADER
═══════════════════════════════════════════ */
.site-header {
    position: fixed;
    top: 0; left: 0; right: 0;
    height: var(--header-h);
    background: rgba(255,255,255,0.96);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border-bottom: 1px solid rgba(0,0,0,0.06);
    z-index: 1000;
}

.header-inner {
    max-width: var(--max-w);
    margin: 0 auto;
    padding: 0 2rem;
    height: 100%;
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.logo {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--charcoal);
    letter-spacing: -0.02em;
    flex-shrink: 0;
}

.desktop-nav {
    display: flex;
    gap: 1.25rem;
    margin-left: auto;
    font-family: var(--font-sans);
}

.desktop-nav a {
    font-size: 0.8rem;
    color: var(--muted);
    font-weight: 500;
    transition: color var(--transition);
    letter-spacing: 0.01em;
    white-space: nowrap;
}
.desktop-nav a:hover  { color: var(--charcoal); }
.desktop-nav a.active { color: var(--saffron); font-weight: 600; }

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 10px;
    margin-left: auto;
}
.hamburger span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--charcoal);
    border-radius: 2px;
    transition: var(--transition);
}

/* ═══════════════════════════════════════════
   MOBILE NAV
═══════════════════════════════════════════ */
.mobile-nav {
    position: fixed;
    top: 0; right: -100%;
    width: min(320px, 85vw);
    height: 100vh;
    background: #fff;
    z-index: 2000;
    padding: 5rem 2.5rem 2.5rem;
    transition: right 0.35s ease;
    box-shadow: -4px 0 24px rgba(0,0,0,0.08);
    overflow-y: auto;
    font-family: var(--font-sans);
}
.mobile-nav.open { right: 0; }

.mobile-nav nav {
    display: flex;
    flex-direction: column;
    gap: 0;
}
.mobile-link {
    display: block;
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--charcoal);
    padding: 0.85rem 0;
    border-bottom: 1px solid #f0f0f0;
    transition: color var(--transition);
}
.mobile-link:hover { color: var(--saffron); }

.mobile-nav-close {
    position: absolute;
    top: 1.5rem; right: 1.5rem;
    background: none;
    border: none;
    font-size: 1.75rem;
    cursor: pointer;
    color: var(--muted);
    line-height: 1;
}

.mobile-nav-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.4);
    z-index: 1999;
}
.mobile-nav-overlay.open { display: block; }

/* ═══════════════════════════════════════════
   SLAB — BASE (reused by future slabs)
═══════════════════════════════════════════ */
.slab { padding: var(--section-py) 0; }

.slab-inner {
    max-width: var(--max-w);
    margin: 0 auto;
    padding: 0 2rem;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

/* ── Alternating image position ── */
.slab-image-left .slab-image { order: -1; }

/* ── Shared image slab styles ── */
.slab .slab-image {
    align-self: stretch;
    border-radius: 6px;
    overflow: hidden;
    min-height: 380px;
    box-shadow: 0 16px 48px rgba(0,0,0,0.10);
}
.slab .slab-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

/* ── Shared text slab styles ── */
.slab .slab-text h2 {
    font-family: var(--font-bengali);
    font-size: clamp(1.6rem, 2.8vw, 2.4rem);
    font-weight: 600;
    line-height: 1.4;
    color: var(--charcoal);
    margin-bottom: 1.25rem;
}
.slab .slab-text p {
    font-family: var(--font-bengali);
    font-size: 1.05rem;
    line-height: 2;
    color: var(--muted);
    margin-bottom: 1rem;
}
.slab .slab-text p:last-child { margin-bottom: 0; }

.slab .slab-subhead {
    font-family: var(--font-sans);
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--charcoal);
    margin-bottom: 1.25rem !important;
}

.slab .slab-cta {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--saffron);
    margin-top: 1.5rem;
}

/* ── Section label (English small caps) ── */
.section-label {
    display: inline-block;
    font-family: var(--font-sans);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--saffron);
    margin-bottom: 1rem;
}

/* ── Pull quote ── */
.pull-quote {
    border-left: 3px solid var(--saffron);
    padding: 0.75rem 1.25rem;
    margin: 1.5rem 0;
    font-family: var(--font-bengali);
    font-size: 1.2rem;
    font-weight: 500;
    font-style: normal;
    color: var(--charcoal);
    line-height: 1.7;
}

/* ── Dark slab variant ── */
.slab-dark {
    background: var(--bg-dark);
    color: #fff;
}
.slab-dark .slab-text h2 { color: #fff; }
.slab-dark .slab-text p  { color: rgba(255,255,255,0.82); }

/* ── Alt background slab ── */
.slab-alt { background: var(--bg-alt); }

/* ═══════════════════════════════════════════
   SLAB 1 — FIRST (FULL-PAGE HERO SLAB)
═══════════════════════════════════════════ */
.slab-first {
    position: relative;
    margin-top: var(--header-h);
    padding: 0;
    min-height: calc(100vh - var(--header-h));
    min-height: calc(100dvh - var(--header-h)); /* dvh excludes mobile browser chrome */
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

/* Dark overlay so text is legible over the photo */
.slab-first::after {
    content: '';
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.52);
    z-index: 1;
}

/* Full-bleed background image */
.slab-bg-image {
    position: absolute;
    inset: 0;
    z-index: 0;
}
.slab-bg-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    object-position: center top;
    display: block;
}

/* Text sits above the overlay */
.slab-first-inner {
    position: relative;
    z-index: 2;
    max-width: 780px;
    padding: 5rem 2rem;
    text-align: left;
}

.slab-first .slab-text h1 {
    font-family: var(--font-bengali);
    font-size: clamp(1.6rem, 3vw, 2.6rem);
    font-weight: 600;
    line-height: 1.5;
    color: #ffffff;
    text-shadow: 0 2px 20px rgba(0,0,0,0.4);
    margin-bottom: 1.5rem;
}

.slab-first .slab-text p {
    font-family: var(--font-bengali);
    font-size: 1.05rem;
    line-height: 2;
    color: rgba(255, 255, 255, 0.88);
    margin-bottom: 1rem;
}
.slab-first .slab-text p:last-child { margin-bottom: 0; }

.slab-first .pull-quote {
    border-left-color: var(--saffron);
    color: #ffffff;
    font-size: 1.25rem;
}

/* ═══════════════════════════════════════════
   FADE-IN ANIMATION
═══════════════════════════════════════════ */
.fade-in {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.7s ease, transform 0.7s ease;
}
.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ═══════════════════════════════════════════
   BACK TO TOP
═══════════════════════════════════════════ */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--saffron);
    color: #fff;
    border: none;
    font-size: 1.1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transform: translateY(8px);
    transition: opacity var(--transition), transform var(--transition), background var(--transition);
    z-index: 900;
}
.back-to-top.visible {
    opacity: 1;
    transform: translateY(0);
}
.back-to-top:hover { background: var(--saffron-dk); }

/* ═══════════════════════════════════════════
   FOOTER
═══════════════════════════════════════════ */
.site-footer {
    background: var(--charcoal);
    color: #fff;
    padding: 4rem 0 0;
    font-family: var(--font-sans);
}

.footer-inner {
    max-width: var(--max-w);
    margin: 0 auto;
    padding: 0 2rem 3rem;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 3rem;
}

.footer-logo {
    font-family: var(--font-serif);
    font-size: 1.2rem;
    font-weight: 700;
    color: #fff;
    display: block;
    margin-bottom: 0.75rem;
}
.footer-tagline {
    font-size: 0.875rem;
    color: #888;
    line-height: 1.6;
    margin-bottom: 1.25rem;
}

.footer-social {
    display: flex;
    gap: 1rem;
}
.social-link {
    font-size: 0.8rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: #aaa;
    border: 1px solid #444;
    padding: 0.3rem 0.75rem;
    border-radius: 3px;
    transition: color var(--transition), border-color var(--transition);
}
.social-link:hover { color: #fff; border-color: #fff; }

.footer-nav-title {
    display: block;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--saffron);
    margin-bottom: 1.25rem;
    font-weight: 700;
}
.footer-nav, .footer-contact {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}
.footer-nav a, .footer-contact a {
    font-size: 0.875rem;
    color: #aaa;
    transition: color var(--transition);
}
.footer-nav a:hover, .footer-contact a:hover { color: #fff; }

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.08);
    text-align: center;
    padding: 1.25rem 2rem;
}
.footer-bottom p {
    font-size: 0.8rem;
    color: #ffffff;
}

/* ═══════════════════════════════════════════
   RESPONSIVE
═══════════════════════════════════════════ */
@media (max-width: 900px) {
    .slab-first-inner { padding: 3.5rem 1.5rem; }
    .slab-inner { grid-template-columns: 1fr; }
    .desktop-nav { display: none; }
    .hamburger   { display: flex; }
    .footer-inner { grid-template-columns: 1fr 1fr; }
    .footer-brand { grid-column: 1 / -1; }
}

@media (max-width: 600px) {
    :root { --section-py: 64px; }
    .slab-first-inner { padding: 2.5rem 1.25rem; }
    .slab-first .slab-text h1 { font-size: 1.45rem; }
    .footer-inner { grid-template-columns: 1fr; }
    .back-to-top { bottom: 1.25rem; right: 1.25rem; }
}