/* ==========================================================================
   1. CORE RESET & HARDWARE ACCELERATION ENGINE
   ========================================================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

:root {
    /* Tông màu chủ đạo theo yêu cầu kỹ thuật */
    --primary-deep: #005f73;
    --electric-cyan: #00f5ff;
    --bg-liquid: #f0f7f9;
    
    /* Thiết lập kính lỏng mờ đặc Light Liquid Glassmorphism */
    --glass-bg: rgba(240, 247, 249, 0.82);
    --glass-border: rgba(255, 255, 255, 0.7);
    --text-main: #1d2d35;
    --text-muted: #4e6570;
    
    /* Hệ thống đổ bóng đa tầng tạo chiều sâu */
    --shadow-soft: 0 8px 32px 0 rgba(0, 95, 115, 0.05);
    --shadow-deep: 0 20px 48px 0 rgba(0, 95, 115, 0.12), 0 2px 8px rgba(0, 0, 0, 0.02);
    
    --radius-lg: 20px;
    --radius-md: 12px;
    --radius-sm: 6px;
    --transition-curve: cubic-bezier(0.16, 1, 0.3, 1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-liquid);
    color: var(--text-main);
    line-height: 1.7;
    overflow-x: hidden;
}

/* Ép tăng tốc phần cứng GPU */
.glass-card, .menu-container, .hero-parallax, .dynamic-island, .faq-trigger {
    transform: translateZ(0);
    backface-visibility: hidden;
    will-change: transform, opacity;
}

/* Typography Đẹp & Hiện Đại Chuẩn UI/UX */
h1, h2, h3, h4, h5, h6 {
    color: var(--primary-deep);
    font-weight: 800;
    line-height: 1.3;
    margin-bottom: 1rem;
}

p {
    color: var(--text-muted);
    margin-bottom: 1.25rem;
    font-size: 1.05rem;
}

blockquote {
    position: relative;
    padding: 1.5rem 2rem;
    background: rgba(0, 95, 115, 0.04);
    border-left: 4px solid var(--electric-cyan);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    font-style: italic;
    margin: 1.5rem 0;
}

ul, ol {
    padding-left: 1.5rem;
    margin-bottom: 1.25rem;
}

li {
    margin-bottom: 0.5rem;
    color: var(--text-muted);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
    border-radius: var(--radius-md);
    transition: transform 0.4s var(--transition-curve);
}

img[alt] {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-style: italic;
}

/* ==========================================================================
   2. LIGHT LIQUID GLASSMORPHISM COMPONENTS
   ========================================================================== */
.glass-card {
    background: var(--glass-bg);
    backdrop-filter: blur(24px) saturate(200%);
    -webkit-backdrop-filter: blur(24px) saturate(200%);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    padding: 3rem 2.5rem;
    box-shadow: var(--shadow-soft);
    transition: all 0.5s var(--transition-curve);
}

.glass-card:hover {
    transform: translateY(-6px) scale(1.01);
    box-shadow: var(--shadow-deep);
    border-color: rgba(0, 245, 255, 0.4);
}

/* Button CTA Cao Cấp */
.btn-cta {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-deep), #007a93);
    color: #ffffff;
    padding: 1.1rem 2.5rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 700;
    font-size: 1rem;
    letter-spacing: 0.5px;
    border: 1px solid rgba(255, 255, 255, 0.15);
    box-shadow: 0 12px 24px rgba(0, 95, 115, 0.18);
    transition: all 0.4s var(--transition-curve);
}

.btn-cta:hover {
    transform: translateY(-3px);
    box-shadow: 0 16px 32px rgba(0, 245, 255, 0.35);
    background: linear-gradient(135deg, #007a93, var(--primary-deep));
}

/* ==========================================================================
   3. UNIFIED NAVIGATION HEADER (DESKTOP & MOBILE CORES)
   ========================================================================== */
.header-nav {
    position: fixed;
    top: 24px;
    left: 50%;
    transform: translateX(-50%);
    width: 92%;
    max-width: 1280px;
    z-index: 9999;
}

.menu-container {
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    padding: 0.6rem 2.5rem;
    border-radius: 100px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow-soft);
    position: relative;
}

.logo img {
    height: 46px;
    width: auto;
}

/* Luồng xử lý hiển thị Menu */
.nav-links {
    display: flex;
    list-style: none;
    gap: 2.2rem;
    align-items: center;
}

.nav-links a {
    color: var(--primary-deep);
    text-decoration: none;
    font-weight: 700;
    font-size: 0.98rem;
    transition: color 0.3s ease;
    position: relative;
}

.nav-links a:hover {
    color: #007a93;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--electric-cyan);
    transition: width 0.3s ease;
}

.nav-links a:hover::after {
    width: 100%;
}

/* Dynamic Island Khối Vật Lý */
.dynamic-island {
    background: #091316;
    color: #ffffff;
    padding: 8px 18px;
    border-radius: 30px;
    font-size: 0.8rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    transition: all 0.6s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.island-dot {
    width: 9px;
    height: 9px;
    background: #34c759;
    border-radius: 50%;
    box-shadow: 0 0 8px #34c759;
}

/* Nút bấm Menu trên Mobile */
.menu-toggle {
    display: none;
    background: var(--primary-deep);
    border: none;
    color: #ffffff;
    padding: 10px 18px;
    border-radius: 30px;
    cursor: pointer;
    align-items: center;
    gap: 8px;
    font-weight: 700;
    font-size: 0.9rem;
    box-shadow: 0 4px 12px rgba(0, 95, 115, 0.2);
    transition: background 0.3s ease;
}

.menu-toggle:hover {
    background: #004d5e;
}

/* ==========================================================================
   4. LAYOUT SYSTEM & GRID CORES
   ========================================================================== */
.container {
    width: 100%;
    max-width: 1240px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section-padding {
    padding: 7rem 0;
}

.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 3.5rem;
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-deep), var(--electric-cyan));
    margin: 12px auto 0 auto;
    border-radius: 2px;
}

/* Parallax Banner */
.hero-parallax {
    position: relative;
    height: 95vh;
    min-height: 680px;
    display: flex;
    align-items: center;
    background-image: linear-gradient(to right, rgba(240, 247, 249, 0.92), rgba(240, 247, 249, 0.75)), url('/img/lam-bang-dai-hoc-gia-re-uy-tin.webp');
    background-attachment: fixed;
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    padding-top: 100px;
}

.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(450px, 1fr)); gap: 3rem; }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 2.5rem; }
.grid-4 { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 1.5rem; }

/* Bảng so sánh */
.comparison-table-wrapper {
    overflow-x: auto;
    background: #ffffff;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-soft);
    border: 1px solid var(--glass-border);
    margin: 2.5rem 0;
}

.comparison-table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
    min-width: 600px;
}

.comparison-table th {
    background: var(--primary-deep);
    color: #ffffff;
    padding: 1.25rem 1.5rem;
    font-weight: 700;
}

.comparison-table td {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid #eef4f6;
    color: var(--text-muted);
}

.comparison-table tr:last-child td { border-bottom: none; }
.comparison-table tr:nth-child(even) { background: #f8fbfb; }

/* Accordion FAQ */
.faq-item {
    background: #ffffff;
    border-radius: var(--radius-md);
    margin-bottom: 1.25rem;
    border: 1px solid rgba(0, 95, 115, 0.08);
    box-shadow: var(--shadow-soft);
}

.faq-trigger {
    width: 100%;
    padding: 1.5rem;
    text-align: left;
    background: none;
    border: none;
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--primary-deep);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-icon {
    font-size: 1.4rem;
    color: var(--electric-cyan);
    transition: transform 0.3s ease;
}

.faq-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    padding: 0 1.5rem;
}

.faq-content p {
    padding-bottom: 1.5rem;
}

/* Cấu trúc Sidebar */
.layout-with-sidebar {
    display: grid;
    grid-template-columns: 1fr 360px;
    gap: 3.5rem;
    padding: 11rem 0 5rem 0;
}

.sidebar-sticky {
    position: sticky;
    top: 120px;
    display: flex;
    flex-direction: column;
    gap: 2.5rem;
}

/* ==========================================================================
   5. UPGRADED DESIGN: DARK LIQUID CHROME FOOTER
   ========================================================================== */
.footer-wrapper {
    background: linear-gradient(180deg, #071114 0%, #03080a 100%);
    color: #92a7b0;
    padding: 6rem 0 2.5rem 0;
    border-top: 2px solid rgba(0, 245, 255, 0.1);
}

.footer-wrapper h4 {
    color: #ffffff;
    font-size: 1.25rem;
    margin-bottom: 1.5rem;
    position: relative;
    padding-bottom: 10px;
}

.footer-wrapper h4::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 35px;
    height: 3px;
    background: var(--electric-cyan);
    border-radius: 2px;
}

.footer-wrapper p {
    color: #92a7b0;
    font-size: 0.95rem;
}

.footer-links {
    list-style: none;
    padding: 0;
}

.footer-links li {
    margin-bottom: 0.8rem;
    color: #92a7b0;
}

.footer-links li a {
    color: #92a7b0;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-links li a:hover {
    color: var(--electric-cyan);
}

/* ==========================================================================
   6. RESPONSIVE COMPACT LAYOUTS (MOBILE & TABLET BREAKPOINTS)
   ========================================================================== */
@media (max-width: 1024px) {
    .layout-with-sidebar {
        grid-template-columns: 1fr;
        gap: 3rem;
    }
    .header-nav {
        width: 95%;
        top: 15px;
    }
    .menu-container {
        padding: 0.5rem 1.5rem;
    }
    
    /* Logic hoán đổi Menu di động */
    .menu-toggle {
        display: flex;
    }
    .dynamic-island {
        display: none; /* Ẩn đảo động vật lý trên Mobile để giảm tải diện tích */
    }
    
    .nav-links {
        position: absolute;
        top: 75px;
        left: 0;
        width: 100%;
        background: rgba(255, 255, 255, 0.98);
        box-shadow: var(--shadow-deep);
        border-radius: var(--radius-lg);
        flex-direction: column;
        padding: 2.5rem 1.5rem;
        gap: 1.8rem;
        opacity: 0;
        visibility: hidden;
        transform: translateY(-20px);
        transition: all 0.4s var(--transition-curve);
        border: 1px solid var(--glass-border);
    }
    
    .nav-links.active {
        opacity: 1;
        visibility: visible;
        transform: translateY(0);
    }
}

@media (max-width: 768px) {
    body { font-size: 0.95rem; }
    .section-padding { padding: 4.5rem 0; }
    .section-title { font-size: 1.9rem; margin-bottom: 2.5rem; }
    .glass-card { padding: 2rem 1.5rem; }
    .grid-2, .grid-3 { grid-template-columns: 1fr; gap: 2rem; }
}