/* ========================================
   TT27 Landing Page – Premium Education UI
   ======================================== */

:root {
    --blue-50: #eff6ff;
    --blue-100: #dbeafe;
    --blue-200: #bfdbfe;
    --blue-500: #3b82f6;
    --blue-600: #2563eb;
    --blue-700: #1d4ed8;
    --blue-800: #1e40af;
    --blue-900: #1e3a5f;

    --slate-50: #f8fafc;
    --slate-100: #f1f5f9;
    --slate-200: #e2e8f0;
    --slate-300: #cbd5e1;
    --slate-400: #94a3b8;
    --slate-500: #64748b;
    --slate-600: #475569;
    --slate-700: #334155;
    --slate-800: #1e293b;
    --slate-900: #0f172a;

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    --shadow-xs: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -1px rgba(0,0,0,0.04);
    --shadow-lg: 0 10px 25px -5px rgba(0,0,0,0.08), 0 8px 10px -6px rgba(0,0,0,0.03);
    --shadow-xl: 0 20px 50px -12px rgba(0,0,0,0.12);

    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; scroll-padding-top: 80px; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    color: var(--slate-700);
    background: #ffffff;
    line-height: 1.7;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

.container { max-width: 1120px; margin: 0 auto; padding: 0 24px; }

/* ─── Scroll Reveal ─── */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.7s ease, transform 0.7s ease;
}
.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ─── Navbar ─── */
.navbar {
    position: sticky;
    top: 0;
    z-index: 1000;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 5%;
    height: 64px;
    background: rgba(255,255,255,0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--slate-200);
    transition: box-shadow var(--transition);
}
.navbar.scrolled { box-shadow: var(--shadow-sm); }

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--blue-700);
    font-weight: 800;
    font-size: 18px;
}
.logo-icon {
    width: 36px; height: 36px;
    display: flex; align-items: center; justify-content: center;
    background: linear-gradient(135deg, var(--blue-600), var(--blue-800));
    border-radius: var(--radius-sm);
    color: white;
    font-size: 18px;
}

.nav-links { display: flex; align-items: center; gap: 28px; }
.nav-links a {
    text-decoration: none;
    color: var(--slate-500);
    font-weight: 500;
    font-size: 14px;
    transition: color var(--transition);
}
.nav-links a:hover { color: var(--blue-700); }

.btn-nav {
    display: inline-flex !important;
    align-items: center;
    gap: 6px;
    padding: 8px 18px !important;
    border-radius: var(--radius-sm) !important;
    background: var(--blue-50) !important;
    color: var(--blue-700) !important;
    font-weight: 600 !important;
    border: 1px solid var(--blue-200);
    transition: background var(--transition), box-shadow var(--transition) !important;
}
.btn-nav:hover { background: var(--blue-100) !important; box-shadow: var(--shadow-xs); }

.mobile-toggle {
    display: none;
    background: none; border: none; cursor: pointer;
    font-size: 24px; color: var(--slate-600);
}

/* ─── Buttons ─── */
.btn {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 12px 24px; border-radius: var(--radius-sm);
    font-weight: 600; font-size: 15px;
    text-decoration: none; cursor: pointer; border: none;
    transition: all var(--transition);
}
.btn-lg { padding: 14px 28px; font-size: 16px; border-radius: var(--radius-md); }

.btn-primary {
    background: linear-gradient(135deg, var(--blue-600), var(--blue-700));
    color: white;
    box-shadow: 0 4px 14px rgba(37,99,235,0.35);
}
.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37,99,235,0.45);
}

.btn-ghost {
    background: white;
    color: var(--slate-700);
    border: 1px solid var(--slate-200);
    box-shadow: var(--shadow-xs);
}
.btn-ghost:hover { background: var(--slate-50); border-color: var(--slate-300); }

.btn-zalo {
    background: #0068ff;
    color: white;
    box-shadow: 0 4px 14px rgba(0,104,255,0.3);
}
.btn-zalo:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0,104,255,0.4); }

.btn-outline-blue {
    background: white;
    color: #0068ff;
    border: 2px solid #0068ff;
}
.btn-outline-blue:hover { background: #eff6ff; }

/* ─── Hero ─── */
.hero {
    position: relative;
    min-height: 85vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 120px 24px 80px;
    overflow: hidden;
    background: linear-gradient(175deg, #f0f7ff 0%, #ffffff 50%, var(--slate-50) 100%);
}

.hero-bg-pattern {
    position: absolute; inset: 0; z-index: 0;
    background-image:
        radial-gradient(circle at 20% 50%, rgba(59,130,246,0.06) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(37,99,235,0.04) 0%, transparent 40%);
}

.hero-content {
    position: relative; z-index: 1;
    text-align: center; max-width: 800px;
}

.badge {
    display: inline-flex; align-items: center; gap: 8px;
    background: white;
    color: var(--blue-700);
    padding: 8px 20px;
    border-radius: 100px;
    font-size: 14px;
    font-weight: 600;
    border: 1px solid var(--blue-200);
    box-shadow: var(--shadow-sm);
    margin-bottom: 32px;
}

.hero h1 {
    font-size: clamp(2.25rem, 5vw, 3.75rem);
    font-weight: 800;
    line-height: 1.15;
    color: var(--slate-900);
    margin-bottom: 24px;
    letter-spacing: -0.5px;
}

.highlight {
    background: linear-gradient(135deg, var(--blue-600), #0ea5e9);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-desc {
    font-size: 1.15rem;
    color: var(--slate-500);
    max-width: 640px;
    margin: 0 auto 36px;
}

.hero-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; margin-bottom: 48px; }

/* Trust bar */
.trust-bar {
    display: inline-flex; align-items: center; gap: 20px;
    background: white;
    padding: 12px 28px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--slate-200);
    box-shadow: var(--shadow-md);
    flex-wrap: wrap; justify-content: center;
}
.trust-item {
    display: flex; align-items: center; gap: 8px;
    font-size: 14px; color: var(--slate-600);
}
.trust-item i { font-size: 20px; color: var(--blue-600); }
.trust-item strong { color: var(--slate-900); }
.trust-divider { width: 1px; height: 24px; background: var(--slate-200); }

/* ─── Sections ─── */
.section { padding: 100px 0; }
.section-alt { background: var(--slate-50); }

.section-header { text-align: center; margin-bottom: 56px; }
.section-label {
    display: inline-block;
    background: var(--blue-50);
    color: var(--blue-700);
    padding: 4px 14px;
    border-radius: 100px;
    font-size: 13px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 16px;
}
.section-header h2 {
    font-size: clamp(1.75rem, 3vw, 2.5rem);
    font-weight: 800;
    color: var(--slate-900);
    line-height: 1.2;
    margin-bottom: 16px;
}
.section-header p {
    font-size: 1.1rem;
    color: var(--slate-500);
    max-width: 560px;
    margin: 0 auto;
}

/* ─── Feature Grid ─── */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.feature-card {
    background: white;
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-lg);
    padding: 36px;
    transition: transform var(--transition), box-shadow var(--transition);
}
.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.feature-icon-wrap {
    width: 56px; height: 56px;
    display: flex; align-items: center; justify-content: center;
    background: linear-gradient(135deg, var(--blue-50), var(--blue-100));
    border-radius: var(--radius-md);
    font-size: 28px;
    color: var(--blue-600);
    margin-bottom: 20px;
}

.feature-card h3 {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--slate-900);
    margin-bottom: 10px;
}
.feature-card p { color: var(--slate-500); font-size: 15px; }

/* ─── Video ─── */
.video-wrapper {
    max-width: 880px;
    margin: 0 auto;
}
.video-frame {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 */
    height: 0;
    border-radius: var(--radius-lg);
    overflow: hidden;
    border: 1px solid var(--slate-200);
    box-shadow: var(--shadow-xl);
    background: var(--slate-900);
}
.video-frame iframe {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
}

/* ─── Steps ─── */
.steps-container {
    max-width: 680px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: stretch;
}

.step-card {
    display: flex;
    gap: 24px;
    background: white;
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-lg);
    padding: 28px 32px;
    transition: box-shadow var(--transition);
}
.step-card:hover { box-shadow: var(--shadow-md); }

.step-number {
    font-size: 2rem;
    font-weight: 800;
    color: var(--blue-600);
    line-height: 1;
    flex-shrink: 0;
    width: 52px;
    opacity: 0.8;
}

.step-content h4 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--slate-900);
    margin-bottom: 8px;
}
.step-content p { color: var(--slate-500); font-size: 15px; }
.step-content code {
    background: var(--blue-50);
    color: var(--blue-700);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 13px;
    font-family: 'SF Mono', 'Consolas', monospace;
}

.step-connector {
    width: 2px;
    height: 32px;
    background: var(--blue-200);
    margin: 0 auto;
    border-radius: 2px;
}

/* ─── FAQ ─── */
.faq-list {
    max-width: 720px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.faq-item {
    background: white;
    border: 1px solid var(--slate-200);
    border-radius: var(--radius-md);
    overflow: hidden;
    transition: box-shadow var(--transition);
}
.faq-item:hover { box-shadow: var(--shadow-sm); }

.faq-question {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 18px 24px;
    background: none;
    border: none;
    cursor: pointer;
    text-align: left;
    font-family: inherit;
    font-size: 15px;
    font-weight: 600;
    color: var(--slate-800);
    transition: background var(--transition);
}
.faq-question:hover { background: var(--slate-50); }
.faq-question i {
    font-size: 18px;
    color: var(--slate-400);
    transition: transform var(--transition);
    flex-shrink: 0;
}
.faq-item.open .faq-question i { transform: rotate(180deg); }

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease, padding 0.4s ease;
}
.faq-item.open .faq-answer {
    max-height: 300px;
}
.faq-answer p {
    padding: 0 24px 20px;
    color: var(--slate-500);
    font-size: 15px;
    line-height: 1.7;
}

/* ─── CTA Box ─── */
.cta-box {
    background: linear-gradient(135deg, var(--blue-600), var(--blue-800));
    border-radius: var(--radius-xl);
    padding: 56px 48px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 40px;
    flex-wrap: wrap;
}
.cta-content h2 { font-size: 1.75rem; font-weight: 800; color: white; margin-bottom: 8px; }
.cta-content p { color: rgba(255,255,255,0.8); font-size: 1.05rem; max-width: 480px; }
.cta-actions { display: flex; gap: 12px; flex-wrap: wrap; }

.cta-box .btn-zalo {
    background: white !important;
    color: #0068ff !important;
    box-shadow: var(--shadow-md) !important;
}
.cta-box .btn-zalo:hover { transform: translateY(-2px); }

.cta-box .btn-outline-blue {
    background: transparent !important;
    border-color: rgba(255,255,255,0.4) !important;
    color: white !important;
}
.cta-box .btn-outline-blue:hover { background: rgba(255,255,255,0.1) !important; }

/* ─── Footer ─── */
.footer {
    background: var(--slate-900);
    color: var(--slate-400);
    padding: 64px 0 0;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 48px;
    padding-bottom: 48px;
    border-bottom: 1px solid rgba(255,255,255,0.08);
}

.footer-brand .logo { color: white; margin-bottom: 16px; }
.footer-brand .logo-icon { background: linear-gradient(135deg, var(--blue-500), var(--blue-700)); }
.footer-brand p { font-size: 14px; line-height: 1.7; max-width: 320px; }

.footer-col { display: flex; flex-direction: column; gap: 12px; }
.footer-col h5 { color: white; font-size: 14px; font-weight: 700; margin-bottom: 4px; text-transform: uppercase; letter-spacing: 0.5px; }
.footer-col a {
    color: var(--slate-400);
    text-decoration: none;
    font-size: 14px;
    display: flex; align-items: center; gap: 6px;
    transition: color var(--transition);
}
.footer-col a:hover { color: white; }

.footer-bottom {
    text-align: center;
    padding: 24px 0;
    font-size: 13px;
    color: var(--slate-500);
}

/* ─── Floating Zalo ─── */
.fab-zalo {
    position: fixed;
    bottom: 28px; right: 28px;
    width: 56px; height: 56px;
    background: #0068ff;
    color: white;
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-size: 26px;
    box-shadow: 0 4px 20px rgba(0,104,255,0.4);
    text-decoration: none;
    z-index: 999;
    transition: transform var(--transition), box-shadow var(--transition);
    animation: fab-pulse 2s ease-in-out infinite;
}
.fab-zalo:hover { transform: scale(1.1); box-shadow: 0 6px 28px rgba(0,104,255,0.5); }

@keyframes fab-pulse {
    0%, 100% { box-shadow: 0 4px 20px rgba(0,104,255,0.4); }
    50% { box-shadow: 0 4px 20px rgba(0,104,255,0.4), 0 0 0 12px rgba(0,104,255,0.08); }
}

/* ─── Responsive ─── */
@media (max-width: 768px) {
    .nav-links { 
        display: none;
        position: absolute;
        top: 64px; left: 0; right: 0;
        flex-direction: column;
        background: white;
        border-bottom: 1px solid var(--slate-200);
        padding: 16px 24px;
        gap: 12px;
        box-shadow: var(--shadow-md);
    }
    .nav-links.open { display: flex; }
    .mobile-toggle { display: block; }

    .feature-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 32px; }
    .cta-box { flex-direction: column; text-align: center; padding: 40px 24px; }
    .cta-actions { justify-content: center; }
    .trust-divider { display: none; }
    .trust-bar { gap: 12px; padding: 16px 20px; }

    .hero { padding: 100px 20px 60px; min-height: auto; }
    .section { padding: 64px 0; }
    .step-card { flex-direction: column; gap: 12px; }
}