* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: all 0.3s ease;
}

:root {
    --primary: #4361ee;
    --secondary: #3f37c9;
    --success: #4caf50;
    --danger: #f44336;
    --warning: #ff9800;
    --dark: #333;
    --light: #f4f4f4;
}

/* Light Theme (Default) */
body.light {
    --bg: #ffffff;
    --text: #333333;
    --card-bg: #ffffff;
    --border: #e0e0e0;
}

/* Dark Theme */
body.dark {
    --bg: #1a1a2e;
    --text: #eeeeee;
    --card-bg: #16213e;
    --border: #0f3460;
    --primary: #4ecdc4;
    --secondary: #45b7d1;
}

/* Ocean Theme */
body.ocean {
    --bg: #e8f4f8;
    --text: #2c3e50;
    --card-bg: #ffffff;
    --border: #b2dfdb;
    --primary: #006064;
    --secondary: #00838f;
}

/* Forest Theme */
body.forest {
    --bg: #e8f5e9;
    --text: #1b5e20;
    --card-bg: #ffffff;
    --border: #a5d6a7;
    --primary: #2e7d32;
    --secondary: #1b5e20;
}

/* Sunset Theme */
body.sunset {
    --bg: #fff3e0;
    --text: #4e342e;
    --card-bg: #ffffff;
    --border: #ffcc80;
    --primary: #e65100;
    --secondary: #bf360c;
}

body {
    background: var(--bg);
    color: var(--text);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
}

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

.navbar {
    background: var(--card-bg);
    border-bottom: 2px solid var(--primary);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary);
    text-decoration: none;
}

.nav-menu {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.nav-menu a {
    color: var(--text);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
}

.nav-menu a:hover {
    background: var(--primary);
    color: white;
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text);
}

.card {
    background: var(--card-bg);
    border-radius: 10px;
    padding: 20px;
    margin-bottom: 20px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    border: 1px solid var(--border);
}

.btn {
    display: inline-block;
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1rem;
    text-decoration: none;
    text-align: center;
}

.btn-primary {
    background: var(--primary);
    color: white;
}

.btn-success {
    background: var(--success);
    color: white;
}

.btn-danger {
    background: var(--danger);
    color: white;
}

.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.slot-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 15px;
    margin: 10px 0;
}

.slot-available {
    border-left: 4px solid var(--success);
}

.slot-full {
    border-left: 4px solid var(--danger);
    opacity: 0.6;
}

@media (max-width: 768px) {
    .nav-toggle {
        display: block;
    }
    
    .nav-menu {
        display: none;
        width: 100%;
        flex-direction: column;
        margin-top: 1rem;
    }
    
    .nav-menu.active {
        display: flex;
    }
    
    .grid {
        grid-template-columns: 1fr;
    }
    
    .container {
        padding: 10px;
    }
}

.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}

.form-control {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border);
    border-radius: 5px;
    background: var(--bg);
    color: var(--text);
}

.alert {
    padding: 15px;
    border-radius: 5px;
    margin-bottom: 20px;
}

.alert-success {
    background: var(--success);
    color: white;
}

.alert-danger {
    background: var(--danger);
    color: white;
}

.alert-warning {
    background: var(--warning);
    color: white;
}

.theme-selector {
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 1000;
}

.theme-selector select {
    padding: 8px;
    border-radius: 5px;
    background: var(--card-bg);
    color: var(--text);
    border: 1px solid var(--border);
}