:root {
    --bg: #0d0d0d;
    --surface: #161616;
    --surface-hover: #1f1f1f;
    --text: #f0f0f0;
    --text-muted: #737373;
    --accent: #60a5fa;
    --border: #262626;
    --shadow: 0 4px 20px rgba(0,0,0,0.4);
}

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

html {
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Inter', 'Segoe UI', system-ui, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

header {
    padding: 1rem;
    border-bottom: 1px solid var(--border);
    background: var(--surface);
}

.header-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    max-width: 1400px;
    margin: 0 auto;
    text-align: center;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
}

.logo-img {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    object-fit: cover;
}

.logo-text {
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--text);
}

.search-box {
    width: 100%;
    max-width: 400px;
}

.search-box input {
    width: 100%;
    padding: 0.625rem 1rem;
    font-size: 0.9375rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text);
    outline: none;
    transition: all 0.2s ease;
    text-align: center;
}

.search-box input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.1);
}

.search-box input::placeholder {
    color: var(--text-muted);
}

.categories {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border);
    background: var(--surface);
}

.category-btn {
    padding: 0.375rem 0.875rem;
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 0.8125rem;
    font-weight: 400;
    transition: all 0.15s ease;
    white-space: nowrap;
    border-radius: 6px;
}

.category-btn:hover {
    color: var(--text);
    background: var(--surface-hover);
}

.category-btn.active {
    color: var(--text);
    background: var(--border);
    font-weight: 500;
}

/* Filter Section */
.filters {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border);
    background: var(--bg);
}

.filter-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.filter-group label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: lowercase;
}

.filter-group select {
    padding: 0.375rem 0.625rem;
    font-size: 0.8125rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    cursor: pointer;
    outline: none;
    min-width: 120px;
}

.filter-group select:focus {
    border-color: var(--accent);
}

.book-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 1rem;
    padding: 1rem;
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
    flex: 1;
}

.book-card {
    background: transparent;
    border-radius: 0;
    border: none;
    transition: transform 0.2s ease, opacity 0.15s ease;
    cursor: pointer;
    text-decoration: none;
    display: block;
    color: inherit;
}

.book-card:hover {
    opacity: 0.85;
}

.book-card:active {
    transform: scale(0.98);
}

.book-cover {
    aspect-ratio: 2/3;
    background: linear-gradient(145deg, #1a1a1a 0%, #0f0f0f 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    border-radius: 6px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: box-shadow 0.2s ease;
}

.book-card:hover .book-cover {
    box-shadow: 0 8px 30px rgba(0,0,0,0.5);
}

.book-cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.book-info {
    padding: 0.5rem 0 0;
}

.book-title {
    font-size: 0.75rem;
    font-weight: 400;
    line-height: 1.35;
    color: var(--text);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    letter-spacing: -0.01em;
}

.book-category {
    font-size: 0.625rem;
    color: var(--text-muted);
    text-transform: lowercase;
    margin-top: 0.125rem;
    letter-spacing: 0.02em;
}

.loading, .error {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--text-muted);
    grid-column: 1 / -1;
    font-size: 0.9375rem;
}

footer {
    padding: 1.25rem;
    border-top: 1px solid var(--border);
    background: var(--surface);
    text-align: center;
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

footer p {
    color: var(--text-muted);
    font-size: 0.8125rem;
}

footer a {
    color: var(--accent);
    text-decoration: none;
    transition: opacity 0.15s ease;
}

footer a:hover {
    opacity: 0.8;
}

/* Buy Me a Coffee Button */
.buymeacoffee-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: #ffdd00;
    color: #000000;
    font-size: 0.8125rem;
    font-weight: 600;
    text-decoration: none;
    border-radius: 6px;
    transition: all 0.15s ease;
}

.buymeacoffee-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(255, 221, 0, 0.3);
    opacity: 1;
}

.buymeacoffee-btn svg {
    width: 16px;
    height: 16px;
}

/* Mobile */
@media (max-width: 640px) {
    header {
        padding: 0.875rem;
    }
    
    .logo-img {
        width: 36px;
        height: 36px;
    }
    
    .logo-text {
        font-size: 1.125rem;
    }
    
    .search-box {
        max-width: none;
    }
    
    .search-box input {
        padding: 0.5rem 0.875rem;
        font-size: 0.875rem;
    }
    
    .book-grid {
        grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
        gap: 0.625rem;
        padding: 0.75rem;
    }
    
    .book-cover {
        border-radius: 4px;
    }
    
    .book-info {
        padding: 0.375rem 0 0;
    }
    
    .book-title {
        font-size: 0.6875rem;
        line-height: 1.3;
    }
    
    .categories {
        justify-content: center;
        padding: 0.5rem;
    }
    
    .category-btn {
        padding: 0.375rem 0.625rem;
        font-size: 0.8125rem;
    }
    
    .filters {
        flex-direction: column;
        align-items: stretch;
        gap: 0.5rem;
    }
    
    .filter-group {
        justify-content: space-between;
    }
    
    .filter-group select {
        flex: 1;
        max-width: 200px;
    }
    
    footer {
        padding: 1rem;
    }
}

@media (max-width: 400px) {
    .book-grid {
        grid-template-columns: repeat(auto-fill, minmax(75px, 1fr));
        gap: 0.5rem;
        padding: 0.625rem;
    }
}

/* Tablet */
@media (min-width: 768px) and (max-width: 1024px) {
    .book-grid {
        grid-template-columns: repeat(auto-fill, minmax(90px, 1fr));
        gap: 0.875rem;
        padding: 1.25rem;
    }
}

/* Large screens */
@media (min-width: 1400px) {
    .book-grid {
        grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
        gap: 1rem;
        padding: 1.5rem;
    }
}
/* Book Counter Styles */
.book-counter-display {
    text-align: center;
    padding: 10px;
    background: var(--accent);
    color: white;
    font-weight: 600;
    font-size: 1.1rem;
    display: none;
}
.book-counter-display {
    text-align: center;
    padding: 10px;
    background: var(--accent);
    color: white;
    font-weight: 600;
    font-size: 1.1rem;
    display: none;
}