:root {
    --primary-color: #d4263e; /* Vietnamese flag red */
    --secondary-color: #ffde00; /* Vietnamese flag yellow */
    --accent-color: #007352; /* Vietnamese jade green */
    --text-color: #333333;
    --bg-color: #ffffff;
    --bg-alt-color: #f8f8f8;
    --footer-color: #222222;
    --card-bg: #ffffff;
    --card-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
    --transition: all 0.3s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Roboto', 'Arial', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

/* Header Styles */
header {
    background-color: var(--bg-color);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
}

.logo-container {
    display: flex;
    align-items: center;
}

.logo-svg {
    height: 40px;
}

nav ul {
    display: flex;
    list-style: none;
}

nav ul li {
    margin-left: 25px;
}

nav ul li a {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

nav ul li a:hover {
    color: var(--primary-color);
}

nav ul li a::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    bottom: -5px;
    left: 0;
    transition: var(--transition);
}

nav ul li a:hover::after {
    width: 100%;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--secondary-color) 0%, var(--primary-color) 100%);
    color: white;
    padding: 140px 0 80px;
    text-align: center;
}

.hero h1 {
    font-size: 2.8rem;
    margin-bottom: 20px;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.hero p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto 30px;
    opacity: 0.9;
}

.cta-button {
    display: inline-block;
    background-color: var(--accent-color);
    color: white;
    padding: 12px 30px;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 700;
    font-size: 1.1rem;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15);
}

.cta-button:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.2);
    background-color: #008f64;
}

/* Features Section */
.features {
    padding: 80px 0;
    background-color: var(--bg-color);
}

.features h2 {
    text-align: center;
    margin-bottom: 50px;
    font-size: 2.2rem;
    color: var(--primary-color);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.feature-card {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 30px;
    text-align: center;
    box-shadow: var(--card-shadow);
    transition: var(--transition);
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.feature-icon {
    margin-bottom: 20px;
}

.feature-card h3 {
    font-size: 1.4rem;
    margin-bottom: 15px;
    color: var(--primary-color);
}

/* How it Works Section */
.how-it-works {
    padding: 80px 0;
    background-color: var(--bg-alt-color);
}

.how-it-works h2 {
    text-align: center;
    margin-bottom: 50px;
    font-size: 2.2rem;
    color: var(--primary-color);
}

.steps {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    margin-bottom: 50px;
}

.step {
    flex: 1;
    min-width: 250px;
    text-align: center;
    padding: 0 20px;
    margin-bottom: 30px;
}

.step-number {
    background-color: var(--primary-color);
    color: white;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    font-size: 1.5rem;
    font-weight: bold;
}

.step h3 {
    font-size: 1.4rem;
    margin-bottom: 15px;
    color: var(--text-color);
}

.cta-container {
    text-align: center;
    margin-top: 40px;
}

/* Tech Details Section */
.tech-details {
    padding: 80px 0;
    background-color: var(--bg-color);
}

.tech-details h2 {
    text-align: center;
    margin-bottom: 50px;
    font-size: 2.2rem;
    color: var(--primary-color);
}

.tech-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.tech-item {
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 25px;
    box-shadow: var(--card-shadow);
    transition: var(--transition);
}

.tech-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
}

.tech-item h3 {
    color: var(--accent-color);
    margin-bottom: 15px;
    font-size: 1.3rem;
}

/* FAQ Section */
.faq {
    padding: 80px 0;
    background-color: var(--bg-alt-color);
}

.faq h2 {
    text-align: center;
    margin-bottom: 50px;
    font-size: 2.2rem;
    color: var(--primary-color);
}

.faq-items {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    margin-bottom: 25px;
    padding: 25px;
    background-color: var(--card-bg);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
}

.faq-item h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: var(--primary-color);
}

/* Footer */
footer {
    background-color: var(--footer-color);
    color: white;
    padding: 50px 0;
}

.footer-content {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

.footer-logo, .footer-links, .footer-contact {
    flex: 1;
    min-width: 250px;
    margin-bottom: 30px;
}

.footer-links h4, .footer-contact h4 {
    color: var(--secondary-color);
    margin-bottom: 20px;
    font-size: 1.2rem;
}

.footer-links ul {
    list-style: none;
}

.footer-links ul li {
    margin-bottom: 10px;
}

.footer-links ul li a {
    color: #ccc;
    text-decoration: none;
    transition: var(--transition);
}

.footer-links ul li a:hover {
    color: white;
    padding-left: 5px;
}

.footer-contact p {
    margin-bottom: 10px;
    color: #ccc;
}

/* Responsive Design */
@media screen and (max-width: 768px) {
    header .container {
        flex-direction: column;
    }
    
    nav ul {
        margin-top: 15px;
    }
    
    nav ul li {
        margin-left: 15px;
        margin-right: 15px;
    }
    
    .hero {
        padding: 180px 0 80px;
    }
    
    .hero h1 {
        font-size: 2.2rem;
    }
    
    .steps {
        flex-direction: column;
    }
    
    .step {
        margin-bottom: 40px;
    }
    
    .footer-content > div {
        flex: 100%;
    }
}

@media screen and (max-width: 480px) {
    .hero h1 {
        font-size: 1.8rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .features h2, .how-it-works h2, .tech-details h2, .faq h2 {
        font-size: 1.8rem;
    }
    
    .cta-button {
        padding: 10px 25px;
        font-size: 1rem;
    }
    
    nav ul {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    nav ul li {
        margin: 5px 10px;
    }
}