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

:root {
    --primary-color: #1e40af;
    --secondary-color: #3b82f6;
    --accent-color: #60a5fa;
    --text-color: #1f2937;
    --text-light: #6b7280;
    --bg-color: #ffffff;
    --bg-light: #f9fafb;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-light);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 700;
}

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

.nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    transition: opacity 0.3s;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
}

.nav-link:hover,
.nav-link.active {
    background-color: rgba(255, 255, 255, 0.2);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.hero-subtitle {
    font-size: 1.25rem;
    opacity: 0.95;
    max-width: 800px;
    margin: 0 auto;
}

/* Section Title */
.section-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--text-color);
}

/* Airlines Section */
.airlines-section {
    padding: 4rem 0;
    background-color: var(--bg-color);
}

.airlines-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem;
}

.airline-card {
    background: white;
    border-radius: 1rem;
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: transform 0.3s, box-shadow 0.3s;
    border: 1px solid var(--border-color);
}

.airline-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.airline-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--border-color);
}

.airline-name {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
}

.airline-code {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 0.875rem;
}

.airline-program {
    font-size: 1rem;
    color: var(--text-light);
    margin-bottom: 1rem;
    font-weight: 500;
}

.benefits-list {
    list-style: none;
    margin-bottom: 1rem;
}

.benefits-list li {
    padding: 0.5rem 0;
    color: var(--text-color);
    font-size: 0.9rem;
}

.airline-tips {
    background: var(--bg-light);
    padding: 1rem;
    border-radius: 0.5rem;
    margin-top: 1rem;
    font-size: 0.9rem;
    line-height: 1.6;
}

.airline-tips strong {
    color: var(--primary-color);
}

/* Tips Section */
.tips-section {
    padding: 4rem 0;
    background: linear-gradient(to bottom, var(--bg-light), white);
}

.tips-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 2rem;
}

.tip-card {
    background: white;
    border-radius: 1rem;
    padding: 2rem;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform 0.3s, box-shadow 0.3s;
    border: 1px solid var(--border-color);
}

.tip-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.tip-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.tip-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.tip-card p {
    color: var(--text-light);
    line-height: 1.6;
}

/* Footer */
.footer {
    background: var(--text-color);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

.footer-text {
    margin-bottom: 0.5rem;
    opacity: 0.9;
}

.footer-icp {
    font-size: 0.875rem;
    opacity: 0.8;
}

.footer-icp a {
    color: white;
    text-decoration: none;
    opacity: 0.8;
    transition: opacity 0.2s;
}

.footer-icp a:hover {
    opacity: 1;
    text-decoration: underline;
}

.footer-divider {
    margin: 0 0.5rem;
    opacity: 0.5;
}

/* Responsive Design */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav {
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .airlines-grid,
    .tips-grid {
        grid-template-columns: 1fr;
    }

    .airline-card,
    .tip-card {
        padding: 1.25rem;
    }
}

/* Smooth Scroll */
html {
    scroll-behavior: smooth;
}

/* Selection */
::selection {
    background-color: var(--accent-color);
    color: white;
}