:root {
    --primary: #4F46E5;
    --secondary: #10B981;
    --accent: #EC4899;
    --light: #F3F4F6;
    --dark: #1F2937;
    --danger: #EF4444;
    --warning: #F59E0B;
    --info: #3B82F6;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    color: #374151;
    background-color: #F9FAFB;
    scroll-behavior: smooth;
}

.gradient-text {
    background: linear-gradient(90deg, var(--primary), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.custom-shadow {
    box-shadow: 0 10px 25px -5px rgba(79, 70, 229, 0.1), 0 10px 10px -5px rgba(79, 70, 229, 0.04);
}

.book-card {
    transition: all 0.3s ease;
}

.book-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 20px 25px -5px rgba(79, 70, 229, 0.1), 0 10px 10px -5px rgba(79, 70, 229, 0.04);
}

.category-card {
    transition: all 0.3s ease;
    background-size: cover;
    background-position: center;
}

.category-card:hover {
    transform: scale(1.03);
}

.btn-primary {
    padding: 0.75rem 1.5rem;
    background-color: var(--primary);
    color: white;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    display: inline-block;
}

.btn-primary:hover {
    background-color: #4338CA;
    transform: translateY(-2px);
}

.btn-secondary {
    padding: 0.75rem 1.5rem;
    background-color: var(--secondary);
    color: white;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    display: inline-block;
}

.btn-secondary:hover {
    background-color: #059669;
    transform: translateY(-2px);
}

.search-box {
    transition: all 0.3s ease;
}

.search-box:focus {
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.3);
}

.pdf-badge {
    position: absolute;
    top: 10px;
    right: 10px;
    background-color: var(--primary);
    color: white;
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 12px;
    font-weight: bold;
}

.menu-item {
    position: relative;
    white-space: nowrap;
    padding: 0.5rem 0;
    font-size: 0.95rem;
}

.menu-item::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: -4px;
    left: 0;
    background-color: var(--secondary);
    transition: width 0.3s ease;
}

.menu-item:hover::after, .menu-item.active::after {
    width: 100%;
}

.mobile-menu {
    transition: transform 0.3s ease-in-out;
    transform: translateX(-100%);
}

.mobile-menu.active {
    transform: translateX(0);
}

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: white;
    min-width: 200px;
    box-shadow: 0 8px 16px rgba(0,0,0,0.1);
    border-radius: 4px;
    z-index: 10;
    top: 100%;
    left: 0;
}

.dropdown:hover .dropdown-content {
    display: block;
}

/* Responsive adjustments */
@media (max-width: 1024px) {
    .grid-cols-4, .grid-cols-3 {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
    .grid-cols-2 {
        grid-template-columns: repeat(1, minmax(0, 1fr));
    }
    
    .book-card img {
        height: 200px;
    }
    
    .hero-section img {
        max-height: 300px;
    }
}

@media (max-width: 768px) {
    .grid-cols-4, .grid-cols-3, .grid-cols-2 {
        grid-template-columns: repeat(1, minmax(0, 1fr));
    }
    
    .book-card img {
        height: 200px;
    }
    
    .hero-section img {
        max-height: 300px;
    }
    
    .adsense-placeholder {
        max-width: 100%;
        height: auto;
    }
}

/* Navigation-specific responsive adjustments */
@media (min-width: 768px) {
    header nav {
        display: flex;
        flex-direction: row;
        flex-wrap: nowrap;
        align-items: center;
        justify-content: center;
        flex: 1;
        padding: 0 1rem;
    }
    .menu-item {
        font-size: 0.95rem;
    }
}

@media (min-width: 1024px) {
    header nav {
        padding: 0 2rem;
    }
    .menu-item {
        font-size: 1rem;
    }
}

/* Lazy loading for images */
img.lazyload {
    opacity: 0;
    transition: opacity 0.3s ease;
}

img.lazyloaded {
    opacity: 1;
}

/* AdSense placeholder */
.adsense-placeholder {
    background-color: #f3f4f6;
    text-align: center;
    padding: 10px;
    margin: 20px 0;
    border-radius: 8px;
    max-width: 728px;
    height: 90px;
}

@media (max-width: 640px) {
    .adsense-placeholder {
        max-width: 100%;
        height: 250px;
    }
}