/* =========================================
   0. THEME OVERRIDES (DARK MODE)
   ========================================= */
[data-theme="dark"] {
    --bg-primary: #1f2937;
    --bg-secondary: #111827;
    --bg-tertiary: #374151;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-tertiary: #9ca3af;
    --border-primary: #374151;
    --border-secondary: #4b5563;
    --accent-primary: #3b82f6;
    --accent-secondary: #60a5fa;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
}

[data-theme="dark"] .header {
    background-color: rgba(31, 41, 55, 0.8);
}

[data-theme="dark"] .difficulty-easy {
    background-color: rgba(34, 197, 94, 0.2);
    color: #4ade80;
    border-color: rgba(34, 197, 94, 0.3);
}

[data-theme="dark"] .difficulty-easy:hover {
    background-color: rgba(34, 197, 94, 0.3);
    border-color: rgba(34, 197, 94, 0.4);
}

[data-theme="dark"] .difficulty-easy.active {
    background-color: #16a34a;
    color: white;
    border-color: #16a34a;
}

[data-theme="dark"] .difficulty-medium {
    background-color: rgba(245, 158, 11, 0.2);
    color: #fbbf24;
    border-color: rgba(245, 158, 11, 0.3);
}

[data-theme="dark"] .difficulty-medium:hover {
    background-color: rgba(245, 158, 11, 0.3);
    border-color: rgba(245, 158, 11, 0.4);
}

[data-theme="dark"] .difficulty-medium.active {
    background-color: #d97706;
    color: white;
    border-color: #d97706;
}

[data-theme="dark"] .difficulty-hard {
    background-color: rgba(239, 68, 68, 0.2);
    color: #f87171;
    border-color: rgba(239, 68, 68, 0.3);
}

[data-theme="dark"] .difficulty-hard:hover {
    background-color: rgba(239, 68, 68, 0.3);
    border-color: rgba(239, 68, 68, 0.4);
}

[data-theme="dark"] .difficulty-hard.active {
    background-color: #dc2626;
    color: white;
    border-color: #dc2626;
}

[data-theme="dark"] .language-php {
    background-color: rgba(139, 92, 246, 0.2);
    color: #a78bfa;
    border-color: rgba(139, 92, 246, 0.3);
}

[data-theme="dark"] .language-php:hover {
    background-color: rgba(139, 92, 246, 0.3);
    border-color: rgba(139, 92, 246, 0.4);
}

[data-theme="dark"] .language-php.active {
    background-color: #8b5cf6;
    color: white;
    border-color: #8b5cf6;
}

[data-theme="dark"] .language-js {
    background-color: rgba(247, 224, 24, 0.2);
    color: #ffe066;
    border-color: rgba(247, 224, 24, 0.3);
}

[data-theme="dark"] .language-js:hover {
    background-color: rgba(247, 224, 24, 0.3);
    border-color: rgba(247, 224, 24, 0.4);
}

[data-theme="dark"] .language-js.active {
    background-color: #ffd60a;
    color: white;
    border-color: #ffd60a;
}

[data-theme="dark"] .language-jsphp {
    background: linear-gradient(90deg, rgba(247, 224, 24, 0.3) 30%, rgba(139, 92, 246, 0.3) 70%);
    color: #ffe066;
    border-color: #a78bfa;
}

[data-theme="dark"] .language-jsphp:hover {
    background: linear-gradient(90deg, rgba(247, 224, 24, 0.4) 30%, rgba(139, 92, 246, 0.4) 70%);
    border-color: #c4b5fd;
}

[data-theme="dark"] .language-jsphp.active {
    background: linear-gradient(90deg, #ffd60a 30%, #8b5cf6 70%);
    color: white;
    border-color: #8b5cf6;
}

[data-theme="dark"] .exam-link-exam {
    background-color: rgba(59, 130, 246, 0.2);
    color: #60a5fa;
}

[data-theme="dark"] .exam-link-exam:hover {
    background-color: rgba(59, 130, 246, 0.3);
}

[data-theme="dark"] .exam-link-solutions {
    background-color: rgba(16, 185, 129, 0.2);
    color: #34d399;
}

[data-theme="dark"] .exam-link-solutions:hover {
    background-color: rgba(16, 185, 129, 0.3);
}

[data-theme="dark"] .exam-link-zip {
    background-color: rgba(245, 158, 11, 0.2);
    color: #fbbf24;
}

[data-theme="dark"] .exam-link-zip:hover {
    background-color: rgba(245, 158, 11, 0.3);
}

[data-theme="dark"] .exam-link-resources {
    background-color: rgba(139, 92, 246, 0.2);
    color: #a78bfa;
}

[data-theme="dark"] .exam-link-resources:hover {
    background-color: rgba(139, 92, 246, 0.3);
}

[data-theme="dark"] .exam-link-grading {
    background-color: rgba(239, 68, 68, 0.2);
    color: #f87171;
}

[data-theme="dark"] .exam-link-grading:hover {
    background-color: rgba(239, 68, 68, 0.3);
}

/* =========================================
   1. RESET & BASE STYLES
   ========================================= */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    transition: background-color 0.2s ease, color 0.2s ease;
}

/* =========================================
   2. LAYOUT
   ========================================= */
.main-content {
    max-width: 1280px;
    margin: 0 auto;
    padding: 1rem 1rem;
}

.content-layout {
    display: flex;
    gap: 2rem;
    flex-direction: column;
}

.content-layout-wrapper {
    display: flex;
    flex-direction: column;
    flex-wrap: wrap;
}

@media (min-width: 1024px) {
    .content-layout {
        flex-direction: row;
    }

    .filter-panel {
        width: 20rem;
        flex-shrink: 0;
    }

    .popular-tags {
        width: 20rem;
        flex-shrink: 0;
    }
}

/* =========================================
   3. HEADER
   ========================================= */
.header {
    position: sticky;
    top: 0;
    z-index: 40;
    backdrop-filter: blur(12px);
    background-color: rgba(255, 255, 255, 0.8);
    border-bottom: 1px solid var(--border-primary);
}

.header-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 4rem;
}

.header-brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.brand-icon {
    display: flex;
    align-items: center;
    justify-content: center;
}

.brand-icon img {
    width: 48px;
    height: 48px;
}

.brand-text h1 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}

.brand-text p {
    display: none;
}

@media (min-width: 512px) {
    .brand-text p {
        display: block;
        font-size: 0.875rem;
        color: var(--text-secondary);
        margin: 0;
    }
}

.header-actions {
    display: flex;
    gap: 12px;
}

.header-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    font-weight: 500;
    padding: 6px;
    border-radius: var(--radius-lg);
    border: none;
    text-decoration: none;
    transition: background 0.2s, box-shadow 0.2s;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    cursor: pointer;
}

.github-btn {
    background: #24292f;
    color: #fff;
}

.github-btn:hover {
    background: #333a41;
}

.github-btn svg {
    margin-right: 6px;
}

.support-btn {
    background: linear-gradient(90deg, #ffb347 0%, #ffcc80 100%);
    color: #222;
}

.support-btn:hover {
    background: linear-gradient(90deg, #ffcc80 0%, #ffb347 100%);
}

/* =========================================
   4. SEARCH SECTION
   ========================================= */
.search-section {
    margin-bottom: 1rem;
    position: sticky;
    top: 10px;
    z-index: 50;
}

@media (max-width: 1200px) {
    .search-section {
        top: 4.75rem;
    }
}

.search-container {
    max-width: 32rem;
    margin: 0 auto;
}

.search-input-wrapper {
    position: relative;
}

.search-icon {
    position: absolute;
    left: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-tertiary);
    pointer-events: none;
}

.search-input {
    width: 100%;
    padding: 0.75rem 0.75rem 0.75rem 2.5rem;
    border: 1px solid var(--border-primary);
    border-radius: var(--radius-xl);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
}

.search-input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

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

/* =========================================
   5. FILTERS & TAGS
   ========================================= */
.filter-panel {
    background-color: var(--bg-primary);
    border-radius: var(--radius-xl);
    border: 1px solid var(--border-primary);
    padding: 1.25rem;
    height: fit-content
}

.filter-header {
    display: flex;
    align-items: center;
    gap: .5rem;
    margin-bottom: 1rem
}

.filter-header svg {
    color: var(--text-secondary)
}

.filter-header h2 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary)
}

.reset-filters {
    padding: 0.5rem;
    border-radius: var(--radius-lg);
    background-color: var(--bg-tertiary);
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}

.reset-filters:hover {
    background-color: var(--border-secondary);
}

.filters {
    display: flex;
    flex-direction: row;
    gap: 1rem
}

.filter-section {
    margin-bottom: 1rem
}

.filter-section:last-child {
    margin-bottom: 0
}

.filter-section h3 {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: .75rem
}

.filter-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: .5rem
}

.filter-btn {
    min-width: 5rem;
    min-height: 1.875rem;
    padding: .375rem .75rem;
    border-radius: var(--radius-lg);
    font-size: .875rem;
    font-weight: 500;
    border: none;
    cursor: pointer;
    background-color: var(--bg-tertiary);
    color: var(--text-secondary)
}

.filter-btn:hover {
    background-color: var(--border-secondary);
    transform: translateY(-1px)
}

.filter-btn.active {
    background-color: var(--accent-primary);
    color: #fff;
    transform: translateY(-1px)
}

.filter-btn:active {
    transform: translateY(0)
}

.hide-completed-btn {
    display: flex;
    align-items: center;
    gap: .75rem;
    width: 100%;
    text-align: left;
    padding: .5rem;
    border-radius: var(--radius-lg);
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-secondary)
}

.hide-completed-btn:hover {
    background-color: var(--bg-secondary)
}

.hide-completed-btn span {
    font-size: .875rem;
    font-weight: 500
}

.hide-completed-btn .eye-off-icon {
    display: none
}

.hide-completed-btn.active .eye-icon {
    display: none
}

.hide-completed-btn.active .eye-off-icon {
    display: block
}

.popular-tags {
    display: flex;
    flex-wrap: wrap;
    flex-direction: row;
    gap: 0.5rem;
    margin-top: 1rem;
}

.filter-pill {
    width: fit-content;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-primary);
    color: var(--text-secondary);
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.2s;
}

.filter-pill:hover {
    background-color: var(--bg-secondary);
    border-color: var(--border-secondary);
    color: var(--text-primary);
}

.filter-pill.active {
    background-color: var(--accent-primary);
    border-color: var(--accent-primary);
    color: #ffffff;
}

/* Difficulty & Language Tags */
.difficulty-easy {
    background-color: #dcfce7;
    color: #166534;
    border: 1px solid #bbf7d0
}

.difficulty-easy:hover {
    background-color: #bbf7d0;
    border-color: #86efac;
    transform: translateY(-1px)
}

.difficulty-easy.active {
    background-color: #16a34a;
    color: #fff;
    border-color: #16a34a
}

.difficulty-medium {
    background-color: #fef3c7;
    color: #92400e;
    border: 1px solid #fde68a
}

.difficulty-medium:hover {
    background-color: #fde68a;
    border-color: #fcd34d;
    transform: translateY(-1px)
}

.difficulty-medium.active {
    background-color: #d97706;
    color: #fff;
    border-color: #d97706
}

.difficulty-hard {
    background-color: #fee2e2;
    color: #991b1b;
    border: 1px solid #fecaca
}

.difficulty-hard:hover {
    background-color: #fecaca;
    border-color: #fca5a5;
    transform: translateY(-1px)
}

.difficulty-hard.active {
    background-color: #dc2626;
    color: #fff;
    border-color: #dc2626
}

.language-php {
    background-color: #f3e8ff;
    color: #7c3aed;
    border: 1px solid #e9d5ff
}

.language-php:hover {
    background-color: #e9d5ff;
    border-color: #ddd6fe;
    transform: translateY(-1px)
}

.language-php.active {
    background-color: #8b5cf6;
    color: #fff;
    border-color: #8b5cf6
}

.language-js {
    background-color: #fef9c3;
    color: #b45309;
    border: 1px solid #fde68a
}

.language-js:hover {
    background-color: #fde68a;
    border-color: #fcd34d;
    transform: translateY(-1px)
}

.language-js.active {
    background-color: #fbbf24;
    color: #fff;
    border-color: #fbbf24
}

.language-jsphp {
    background: linear-gradient(90deg, #fef9c3 30%, #f3e8ff 70%);
    color: #7c3aed;
    border: 1px solid #bdb2ff
}

.language-jsphp:hover {
    background: linear-gradient(90deg, #fde68a 30%, #e9d5ff 70%);
    border-color: #a78bfa;
    transform: translateY(-1px)
}

.language-jsphp.active {
    background: linear-gradient(90deg, #fbbf24 30%, #8b5cf6 70%);
    color: #fff;
    border-color: #8b5cf6
}

/* =========================================
   6. RESULTS GRID
   ========================================= */
.results-section {
    flex: 1;
}

.results-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1rem;
}

.results-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.results-count {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.results-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.25rem;
}

@media (min-width: 560px) {
    .results-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1280px) {
    .results-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

.no-results {
    text-align: center;
    padding: 3rem 0;
}

.no-results svg {
    color: var(--text-tertiary);
    margin: 0 auto 1rem;
}

.no-results h3 {
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.no-results p {
    color: var(--text-secondary);
}

/* =========================================
   7. EXAM CARD
   ========================================= */
.exam-card {
    background-color: var(--bg-primary);
    border-radius: var(--radius-xl);
    border: 1px solid var(--border-primary);
    overflow: hidden;
    animation: slideUp .3s ease-out
}

.exam-card:hover {
    box-shadow: 0 4px 6px -1px rgb(0 0 0/.1), 0 2px 4px -2px rgb(0 0 0/.1)
}

.exam-card.completed {
    opacity: .75
}

.exam-thumbnail {
    position: relative;
    aspect-ratio: 16/9;
    background-color: var(--bg-tertiary);
    overflow: hidden
}

.exam-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    cursor: pointer;
    transition: transform .2s ease
}

.exam-thumbnail:hover img {
    transform: scale(1.05)
}

.no-thumbnail {
    width: 100%;
    height: 100%;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    color: var(--text-tertiary);
    font-size: 1rem;
    font-weight: 500;
    text-align: center;
    border-radius: var(--radius-lg)
}

.thumbnail-overlay {
    position: absolute;
    inset: 0;
    background-color: rgba(0, 0, 0, 0);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0
}

.thumbnail-overlay:hover {
    background-color: rgba(0, 0, 0, .1);
    opacity: 1
}

.thumbnail-overlay svg {
    color: #fff;
    width: 2rem;
    height: 2rem
}

.completion-checkbox {
    position: absolute;
    top: .75rem;
    right: .75rem;
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    border: 2px solid rgba(255, 255, 255, .8);
    background-color: rgba(255, 255, 255, .8);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer
}

.completion-checkbox:hover {
    background-color: #fff;
    border-color: #fff
}

.completion-checkbox.completed {
    background-color: var(--success);
    border-color: var(--success);
    color: #fff
}

.exam-content {
    padding: 1.5rem
}

.exam-header {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    margin-bottom: .5rem
}

.exam-title {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: .5rem;
}

.exam-title h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    line-height: 1.4;
    line-clamp: 2;
}

.exam-code {
    display: flex;
    align-items: center;
    gap: .375rem;
    width: fit-content;
    font-family: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, 'Courier New', monospace;
    font-size: .875rem;
    color: var(--accent-primary);
    cursor: pointer;
    transition: color .2s ease;
    background-color: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: .25rem .5rem;
    border: 1px solid var(--border-primary);
    white-space: nowrap;
}

.exam-code:hover {
    color: var(--accent-secondary);
    background-color: var(--bg-secondary);
}

.exam-code svg {
    margin-left: .5rem;
}

.exam-formula {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
}

.exam-metadata {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: .875rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    flex-wrap: wrap
}

.exam-metadata-item {
    display: flex;
    align-items: center;
    gap: .25rem
}

.exam-metadata-item svg {
    width: 1rem;
    height: 1rem
}

.exam-badge {
    padding: .25rem .5rem;
    border-radius: 9999px;
    font-size: .75rem;
    font-weight: 500
}

.exam-tags {
    display: flex;
    align-items: flex-start;
    gap: .5rem;
    margin-bottom: 1rem
}

.exam-tags svg {
    width: 1rem;
    height: 1rem;
    color: var(--text-tertiary);
    margin-top: .125rem;
    flex-shrink: 0
}

.exam-tags-list {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: .25rem
}

.exam-tag {
    padding: .25rem .5rem;
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
    font-size: .75rem;
    border-radius: var(--radius-md);
    border: none;
    cursor: default
}

.exam-tag-expand,
.exam-tag-collapse {
    cursor: pointer;
    background-color: var(--accent-primary);
    color: #fff
}

.exam-tag-expand:hover,
.exam-tag-collapse:hover {
    background-color: var(--accent-secondary);
    transform: translateY(-1px)
}

.exam-links {
    display: flex;
    flex-wrap: wrap;
    gap: .5rem
}

.exam-link {
    display: inline-flex;
    align-items: center;
    gap: .25rem;
    padding: .375rem .5rem;
    font-size: .75rem;
    font-weight: 500;
    border-radius: var(--radius-lg);
    text-decoration: none
}

.exam-link svg {
    width: .75rem;
    height: .75rem
}

.exam-link-exam {
    background-color: #dbeafe;
    color: #1d4ed8
}

.exam-link-exam:hover {
    background-color: #bfdbfe;
    transform: translateY(-1px)
}

.exam-link-solutions {
    background-color: #dcfce7;
    color: #166534
}

.exam-link-solutions:hover {
    background-color: #bbf7d0;
    transform: translateY(-1px)
}

.exam-link-zip {
    background-color: #fef3c7;
    color: #92400e
}

.exam-link-zip:hover {
    background-color: #fde68a;
    transform: translateY(-1px)
}

.exam-link-resources {
    background-color: #f3e8ff;
    color: #7c3aed
}

.exam-link-resources:hover {
    background-color: #e9d5ff;
    transform: translateY(-1px)
}

.exam-link-grading {
    background-color: #fee2e2;
    color: #991b1b
}

.exam-link-grading:hover {
    background-color: #fecaca;
    transform: translateY(-1px)
}

/* =========================================
   8. MODAL
   ========================================= */
.modal {
    position: fixed;
    inset: 0;
    z-index: 50;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem
}

.modal-backdrop {
    position: absolute;
    inset: 0;
    background-color: rgba(0, 0, 0, .8);
    backdrop-filter: blur(4px)
}

.modal-content {
    position: relative;
    max-width: 64rem;
    max-height: 90vh;
    background-color: var(--bg-primary);
    border-radius: var(--radius-xl);
    overflow: hidden
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem;
    border-bottom: 1px solid var(--border-primary)
}

.modal-title h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0
}

.modal-title p {
    font-size: .875rem;
    color: var(--text-secondary);
    margin: 0
}

.modal-close {
    padding: .5rem;
    border-radius: var(--radius-lg);
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-tertiary)
}

.modal-close:hover {
    background-color: var(--bg-tertiary);
    color: var(--text-secondary)
}

.modal-image {
    overflow: auto;
    max-height: 70vh
}

.modal-image img {
    width: 100%;
    height: auto;
    object-fit: contain
}

/* =========================================
   9. UTILITIES & ANIMATIONS
   ========================================= */
@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes zoomIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

.slide-up {
    animation: slideUp 0.3s ease-out;
}