/* ===== CSS Variables cho Theme Dark Premium ===== */
:root {
    --bg-primary: #0f172a;      /* Xanh đen đậm */
    --bg-secondary: #1e293b;    /* Xanh nhạt hơn cho card */
    --text-main: #f8fafc;       /* Trắng sáng */
    --text-muted: #94a3b8;      /* Xám nhạt */
    --accent-color: #0ea5e9;    /* Xanh lam sáng */
    --accent-glow: rgba(14, 165, 233, 0.5);
    --border-color: #334155;
    --transition: all 0.3s ease;
}

/* ===== Reset & Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

ul {
    list-style: none;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

.section-padding {
    padding: 100px 0;
}

.text-center {
    text-align: center;
}

.mx-auto {
    margin-left: auto;
    margin-right: auto;
}

/* ===== Typography ===== */
h1, h2, h3, h4 {
    font-weight: 700;
    line-height: 1.2;
}

.highlight {
    color: var(--accent-color);
    text-shadow: 0 0 15px var(--accent-glow);
}

.section-title h2 {
    font-size: 2.5rem;
    margin-bottom: 10px;
}

.line {
    width: 60px;
    height: 4px;
    background: var(--accent-color);
    margin-bottom: 20px;
    border-radius: 2px;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 12px 30px;
    border-radius: 30px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}

.btn-primary {
    background-color: var(--accent-color);
    color: #fff;
    box-shadow: 0 4px 15px var(--accent-glow);
}

.btn-primary:hover {
    background-color: #0284c7;
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--accent-glow);
}

.btn-secondary {
    background-color: transparent;
    border-color: var(--text-main);
    color: var(--text-main);
}

.btn-secondary:hover {
    background-color: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

.btn-outline {
    border: 1px solid var(--accent-color);
    padding: 8px 20px;
    border-radius: 20px;
    color: var(--accent-color);
}

.btn-outline:hover {
    background-color: var(--accent-color);
    color: #fff;
    box-shadow: 0 0 10px var(--accent-glow);
}

/* ===== Navigation ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 20px 0;
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo-az {
    background: var(--accent-color);
    color: #fff;
    padding: 4px 8px;
    border-radius: 4px;
}

.logo-text {
    letter-spacing: 1px;
}

.nav-links {
    display: flex;
    gap: 30px;
    align-items: center;
}

.nav-links a:hover:not(.btn-outline) {
    color: var(--accent-color);
}

/* ===== Hero Section ===== */
.hero {
    height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    background: radial-gradient(circle at center, #1e293b 0%, #0f172a 100%);
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: linear-gradient(rgba(15, 23, 42, 0.7), rgba(15, 23, 42, 0.9)), 
                      url('data:image/svg+xml;utf8,<svg width="20" height="20" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><circle cx="2" cy="2" r="1" fill="rgba(255,255,255,0.05)"/></svg>');
    z-index: 1;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
    text-align: center;
    margin: 0 auto;
}

.hero h1 {
    font-size: 4rem;
    margin-bottom: 20px;
}

.hero p {
    font-size: 1.2rem;
    color: var(--text-muted);
    margin-bottom: 40px;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 20px;
}

/* ===== About Section ===== */
.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
    margin-top: 40px;
}

.about-text h3 {
    font-size: 1.5rem;
    color: var(--accent-color);
}

.about-text p {
    color: var(--text-muted);
    margin-bottom: 15px;
}

.stats {
    display: flex;
    gap: 30px;
    margin-top: 30px;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
}

.stat-item {
    text-align: center;
}

.stat-item i {
    font-size: 2rem;
    color: var(--accent-color);
    margin-bottom: 10px;
}

.stat-item h4 {
    font-size: 1.1rem;
    margin-bottom: 5px;
}

.stat-item p {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.image-placeholder {
    width: 100%;
    height: 400px;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, #2dd4bf 100%);
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 20px 40px rgba(0,0,0,0.3);
    position: relative;
}

.image-placeholder::after {
    content: '';
    position: absolute;
    inset: -2px;
    border-radius: 22px;
    background: linear-gradient(45deg, var(--accent-color), transparent, var(--accent-color));
    z-index: -1;
    animation: borderGlow 3s linear infinite;
}

.image-placeholder i {
    font-size: 8rem;
    color: rgba(255,255,255,0.2);
}

@keyframes borderGlow {
    0% { filter: hue-rotate(0deg); }
    100% { filter: hue-rotate(360deg); }
}

@keyframes float {
    0% { transform: translateY(0px); box-shadow: 0 20px 40px rgba(0,0,0,0.4); }
    50% { transform: translateY(-15px); box-shadow: 0 30px 50px rgba(0,0,0,0.6); }
    100% { transform: translateY(0px); box-shadow: 0 20px 40px rgba(0,0,0,0.4); }
}

/* ===== Services Section ===== */
.services {
    background-color: var(--bg-secondary);
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 50px;
}

.service-card {
    background: var(--bg-primary);
    padding: 40px 30px;
    border-radius: 15px;
    border: 1px solid var(--border-color);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.service-card:hover {
    transform: translateY(-10px);
    border-color: var(--accent-color);
    box-shadow: 0 10px 30px rgba(14, 165, 233, 0.1);
}

.icon-box {
    width: 70px;
    height: 70px;
    background: rgba(14, 165, 233, 0.1);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 25px;
}

.icon-box i {
    font-size: 2rem;
    color: var(--accent-color);
}

.service-card h3 {
    margin-bottom: 15px;
    font-size: 1.3rem;
}

.service-card p {
    color: var(--text-muted);
}

/* ===== Footer ===== */
.footer {
    background-color: #0b1120;
    padding: 60px 0 20px;
    border-top: 1px solid var(--border-color);
}

.footer-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-about h3, .footer-contact h3 {
    color: var(--accent-color);
    margin-bottom: 20px;
}

.footer-about p {
    color: var(--text-muted);
    max-width: 400px;
}

.footer-contact ul li {
    color: var(--text-muted);
    margin-bottom: 15px;
    display: flex;
    align-items: flex-start;
    gap: 15px;
}

.footer-contact ul li i {
    color: var(--accent-color);
    margin-top: 5px;
}

.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* ===== Responsive Design ===== */
@media (max-width: 992px) {
    .about-content {
        grid-template-columns: 1fr;
    }
    
    .hero h1 {
        font-size: 3rem;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none; /* Trong thực tế sẽ làm hamburger menu, làm ẩn tạm thời cho bản đơn giản */
    }
    
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .stats {
        flex-direction: column;
        gap: 20px;
    }
}