:root {
    --primary-color: #4CAF50;
    --primary-dark: #388E3C;
    --primary-light: #C8E6C9;
    --accent-color: #8BC34A;
    --text-primary: #212121;
    --text-secondary: #757575;
    --divider-color: #BDBDBD;
    --background: #FFFFFF;
}

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

.bg-green {
    background-color: var(--primary-color) !important;
}

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

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

.text-green {
    color: var(--primary-color) !important;
}

.dropdown-submenu {
    position: relative;
}

.dropdown-submenu .dropdown-menu {
    top: 0;
    left: 100%;
    margin-top: -1px;
}

.navbar {
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.card {
    border: none;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    transition: transform 0.3s ease;
    margin-bottom: 20px;
}

.card:hover {
    transform: translateY(-5px);
}

.card-img-top {
    height: 180px;
    object-fit: cover;
}

.category-card {
    border-left: 4px solid var(--primary-color);
}

.pagination .page-item.active .page-link {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
}

.pagination .page-link {
    color: var(--primary-color);
}

.question-image, .option-image, .explanation-image {
    max-width: 100%;
    max-height: 300px;
    margin: 10px 0;
    border: 1px solid var(--divider-color);
    border-radius: 4px;
}

@media (max-width: 768px) {
    .navbar-nav .dropdown-menu {
        position: static;
        float: none;
    }
    
    .dropdown-submenu .dropdown-menu {
        position: static;
        margin-left: 15px;
    }
    
    .card-img-top {
        height: 120px;
    }
}