:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --warning-color: #f39c12;
    --success-color: #27ae60;
}

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

.hero-section {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

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

.card {
    border: none;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.08);
    transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
}

.number-ball {
    display: inline-block;
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border-radius: 50%;
    text-align: center;
    line-height: 40px;
    font-weight: bold;
    margin: 0 2px;
}

.sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    z-index: 100;
    padding: 48px 0 0;
    box-shadow: inset -1px 0 0 rgba(0, 0, 0, .1);
}

.sidebar .nav-link {
    font-weight: 500;
    color: #333;
    padding: 0.75rem 1rem;
}

.sidebar .nav-link.active {
    color: var(--primary-color);
    background-color: #e9ecef;
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        position: static;
        height: auto;
    }
}