:root {
    /* Modern Color Palette */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --dark-bg: #0f0f23;
    --card-bg: rgba(255, 255, 255, 0.05);
    --card-border: rgba(255, 255, 255, 0.1);
    --text-primary: #ffffff;
    --text-secondary: #b4b4c5;
    --accent-purple: #667eea;
    --accent-pink: #f5576c;
    --accent-cyan: #00f2fe;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 20px rgba(102, 126, 234, 0.3);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--dark-bg);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    background-image: 
        radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(245, 87, 108, 0.1) 0%, transparent 50%);
}

/* Navigation */
nav {
    background: var(--card-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--card-border);
    padding: var(--spacing-sm) var(--spacing-lg);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-links {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.3s ease;
    font-weight: 500;
}

.nav-links a:hover {
    color: var(--text-primary);
}

.nav-user {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Dropdown Menu */
.nav-dropdown {
    position: relative;
}

.nav-dropdown-toggle {
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.nav-dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    margin-top: 0.75rem;
    background: #1a1a2e;
    border: 1px solid var(--card-border);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-lg);
    min-width: 180px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity 0.3s ease, transform 0.3s ease, visibility 0.3s;
    z-index: 1000;
}

.nav-dropdown:hover .nav-dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.nav-dropdown-menu a {
    display: block;
    padding: 0.75rem 1rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition: background 0.2s ease, color 0.2s ease;
    font-size: 0.95rem;
}

.nav-dropdown-menu a:first-child {
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
}

.nav-dropdown-menu a:last-child {
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
}

.nav-dropdown-menu a:hover {
    background: rgba(102, 126, 234, 0.1);
    color: var(--text-primary);
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-lg);
}

/* Cards */
.card {
    background: var(--card-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.card-header {
    margin-bottom: var(--spacing-lg);
}

.card-title {
    font-size: 2rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.card-subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Forms */
.form-group {
    margin-bottom: var(--spacing-md);
}

.form-label {
    display: block;
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 0.9rem;
}

.form-input,
.form-select {
    width: 100%;
    padding: var(--spacing-sm);
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-size: 1rem;
    transition: all 0.3s ease;
}

.form-select {
    background: #1a1a2e;
    cursor: pointer;
}

.form-select option {
    background: #1a1a2e;
    color: var(--text-primary);
    padding: var(--spacing-sm);
}

.form-input:focus,
.form-select:focus {
    outline: none;
    border-color: var(--accent-purple);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.form-input::placeholder {
    color: var(--text-secondary);
    opacity: 0.5;
}

/* Buttons */
.btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    display: inline-block;
    text-align: center;
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
    box-shadow: var(--shadow-glow);
    transform: translateY(-2px);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    border: 1px solid var(--card-border);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.15);
}

.btn-full {
    width: 100%;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Flash Messages */
.flash-messages {
    max-width: 1200px;
    margin: var(--spacing-md) auto;
    padding: 0 var(--spacing-lg);
}

.flash {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-sm);
    margin-bottom: var(--spacing-sm);
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.flash-success {
    background: rgba(79, 172, 254, 0.2);
    border-left: 4px solid var(--accent-cyan);
}

.flash-error {
    background: rgba(245, 87, 108, 0.2);
    border-left: 4px solid var(--accent-pink);
}

.flash-warning {
    background: rgba(255, 193, 7, 0.2);
    border-left: 4px solid #ffc107;
}

.flash-info {
    background: rgba(102, 126, 234, 0.2);
    border-left: 4px solid var(--accent-purple);
}

/* Grid */
.grid {
    display: grid;
    gap: var(--spacing-md);
}

.grid-2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
    grid-template-columns: repeat(3, 1fr);
}

/* Loading Spinner */
.spinner {
    border: 3px solid rgba(255, 255, 255, 0.1);
    border-top: 3px solid var(--accent-purple);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
    margin: 0 auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Tabs */
.tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--card-border);
}

.tab {
    padding: var(--spacing-sm) var(--spacing-md);
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    border-bottom: 2px solid transparent;
    transition: all 0.3s ease;
}

.tab.active {
    color: var(--text-primary);
    border-bottom-color: var(--accent-purple);
}

.tab:hover {
    color: var(--text-primary);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* Flight Results */
.flight-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    transition: all 0.3s ease;
}

.flight-card:hover {
    border-color: var(--accent-purple);
    box-shadow: var(--shadow-glow);
}

.flight-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.flight-price {
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--success-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.flight-details {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.airline-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: rgba(102, 126, 234, 0.2);
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    margin-right: var(--spacing-xs);
    margin-bottom: var(--spacing-xs);
}

/* Filters */
.filters {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.filter-group {
    margin-bottom: var(--spacing-md);
}

.filter-title {
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.checkbox-group {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    padding: var(--spacing-xs) var(--spacing-sm);
    background: rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-sm);
    transition: all 0.3s ease;
}

.checkbox-label:hover {
    background: rgba(255, 255, 255, 0.1);
}

.checkbox-label input[type="checkbox"] {
    cursor: pointer;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }
    
    .nav-container {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .grid-2,
    .grid-3 {
        grid-template-columns: 1fr;
    }
}