:root {
    --bg-color: #FAFAFA;
    --card-bg: #FFFFFF;
    --text-primary: #111827;
    --text-secondary: #4B5563;
    --border-color: #E5E7EB;
    --accent-color: #2563EB;
    --accent-hover: #1D4ED8;
    --focus-ring: rgba(37, 99, 235, 0.5);
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius: 12px;
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Header & Search */
.header {
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 2rem 0;
    margin-bottom: 3rem;
    position: sticky;
    top: 0;
    z-index: 10;
    box-shadow: var(--shadow-sm);
}

.header h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    text-align: center;
}

.search-container {
    position: relative;
    max-width: 600px;
    margin: 0 auto;
}

.search-container input {
    width: 100%;
    padding: 1rem 1rem 1rem 3rem;
    font-size: 1.125rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    background-color: var(--bg-color);
    color: var(--text-primary);
    transition: var(--transition);
}

.search-container input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px var(--focus-ring);
    background-color: var(--card-bg);
}

.search-icon {
    position: absolute;
    left: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

/* Grid Layout */
.homework-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.card {
    background-color: var(--card-bg);
    border-radius: var(--radius);
    overflow: hidden;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

.card:hover, .card:focus-within {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-color);
}

.card:focus-within {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

.card-image-wrapper {
    width: 100%;
    aspect-ratio: 4/3;
    overflow: hidden;
    background-color: #f3f4f6;
    display: flex;
    align-items: center;
    justify-content: center;
}

.card-image {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s ease;
}

.card:hover .card-image {
    transform: scale(1.05);
}

.card-content {
    padding: 1.25rem;
}

.card-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}


/* Pagination */
.pagination-container {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1.5rem;
    margin-bottom: 4rem;
}

.btn {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-primary);
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

.btn:hover:not(:disabled) {
    background-color: var(--bg-color);
    border-color: var(--text-primary);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.page-info {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
}

/* Utils */
.hidden {
    display: none !important;
}

#noResults {
    text-align: center;
    font-size: 1.25rem;
    color: var(--text-secondary);
    padding: 3rem 0;
}

/* Lightbox Modal */
.lightbox {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.9);
    z-index: 100;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.lightbox:not(.hidden) {
    opacity: 1;
    visibility: visible;
}

.lightbox-close {
    position: absolute;
    top: 1.5rem;
    right: 2rem;
    background: transparent;
    border: none;
    color: white;
    font-size: 3rem;
    cursor: pointer;
    transition: color 0.2s;
    line-height: 1;
    z-index: 101;
}

.lightbox-close:hover {
    color: var(--accent-color);
}

.lightbox-content {
    max-width: 90vw;
    max-height: 90vh;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.lightbox-content img {
    max-width: 100%;
    max-height: 80vh;
    object-fit: contain;
    border-radius: 8px;
    box-shadow: 0 0 20px rgba(0,0,0,0.5);
}

.lightbox-content h2 {
    color: white;
    margin-top: 1.5rem;
    font-size: 1.5rem;
    font-weight: 500;
}