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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: #f8f9fa;
}

/* Navigation */
.navbar {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 1rem 0;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
}

.logo {
    color: white;
    font-size: 1.8rem;
    font-weight: bold;
    text-decoration: none;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: #ffd700;
}

/* Main Content */
.main-content {
    margin-top: 80px;
    padding: 2rem;
}

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

.page-header {
    text-align: center;
    margin-bottom: 3rem;
}

.page-header h1 {
    font-size: 2.5rem;
    color: #333;
    margin-bottom: 1rem;
}

.page-header p {
    color: #666;
    font-size: 1.1rem;
}

/* Buttons */
.btn {
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
}

.btn-primary {
    background: #667eea;
    color: white;
}

.btn-primary:hover {
    background: #5a6fd8;
    transform: translateY(-2px);
}

.btn-secondary {
    background: #6c757d;
    color: white;
}

.btn-secondary:hover {
    background: #5a6268;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        gap: 1rem;
    }
    
    .page-header h1 {
        font-size: 2rem;
    }
}