/* ===                      === */
/* === CSS Variables        === */
/* ===                      === */
:root {
    --primary-color: #4361ee;
    --primary-light: rgba(67, 97, 238, 0.1);
    --primary-light-solid: #edf2ff;
    --primary-dark: #3a56d4;
    --secondary-color: #7209b7;
    --success-color: #2ecc71;
    --warning-color: #f39c12;
    --danger-color: #e74c3c;
    --dark-color: #1a1a2e;
    --light-color: #ffffff;
    --gray-50: #f8fafc;
    --gray-100: #f1f5f9;
    --gray-200: #e2e8f0;
    --gray-300: #cbd5e1;
    --gray-400: #94a3b8;
    --gray-500: #64748b;
    --gray-600: #475569;
    --gray-700: #334155;
    --gray-800: #1e293b;
    --gray-900: #0f172a;
    
    --border-radius: 16px;
    --border-radius-sm: 8px;
    --border-radius-lg: 24px;
    
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 20px rgba(0,0,0,0.08);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
    --shadow-xl: 0 20px 40px rgba(0,0,0,0.15);
    
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.5s ease;
    
    --container-max: 1400px;
    --content-width: 800px;
    --sidebar-width: 360px;
}

/* ===                      === */
/* === Reset & Base         === */
/* ===                      === */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--gray-800);
    background: var(--gray-50);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ===                      === */
/* === Article Detail Page  === */
/* ===                      === */

/* Main Container */
.article-detail-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px 60px;
}

/* Breadcrumb */
.article-breadcrumb {
    padding: 24px 0;
}

.breadcrumb-container {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
    color: var(--gray-500);
    flex-wrap: wrap;
}

.breadcrumb-item {
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--gray-500);
    text-decoration: none;
    padding: 6px 10px;
    border-radius: var(--border-radius-sm);
    transition: var(--transition-fast);
}

.breadcrumb-item:hover {
    background: var(--gray-100);
    color: var(--primary-color);
}

.breadcrumb-icon {
    flex-shrink: 0;
}

.breadcrumb-arrow {
    color: var(--gray-300);
    flex-shrink: 0;
}

.breadcrumb-current {
    color: var(--gray-700);
    font-weight: 500;
    padding: 6px 10px;
}

/* Main Layout */
.article-layout {
    display: grid;
    grid-template-columns: 1fr var(--sidebar-width);
    gap: 40px;
    align-items: start;
}

@media (max-width: 1200px) {
    .article-layout {
        grid-template-columns: 1fr;
        gap: 32px;
    }
}

/* Article Header */
.article-header-section {
    background: var(--light-color);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    margin-bottom: 32px;
}

.article-hero-image {
    position: relative;
    width: 100%;
    height: 400px;
    overflow: hidden;
}

.article-hero-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.6s ease;
}

.article-header-section:hover .article-hero-image img {
    transform: scale(1.02);
}

.featured-badge {
    position: absolute;
    top: 20px;
    right: 20px;
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    color: white;
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 6px;
    box-shadow: var(--shadow-md);
}

.article-header-content {
    padding: 32px;
}

.article-meta-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    flex-wrap: wrap;
    gap: 12px;
}

.article-categories {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.category-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    background: var(--primary-light);
    color: var(--primary-color);
    border-radius: 20px;
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    transition: var(--transition-fast);
    border: 1px solid transparent;
}

.category-badge:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-1px);
}

.difficulty-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.difficulty-beginner {
    background: rgba(46, 204, 113, 0.1);
    color: var(--success-color);
    border: 1px solid rgba(46, 204, 113, 0.3);
}

.difficulty-intermediate {
    background: rgba(243, 156, 18, 0.1);
    color: var(--warning-color);
    border: 1px solid rgba(243, 156, 18, 0.3);
}

.difficulty-advanced {
    background: rgba(231, 76, 60, 0.1);
    color: var(--danger-color);
    border: 1px solid rgba(231, 76, 60, 0.3);
}

.article-title {
    font-size: 40px;
    font-weight: 800;
    line-height: 1.2;
    color: var(--gray-900);
    margin-bottom: 16px;
    word-wrap: break-word;
}

.article-excerpt {
    font-size: 18px;
    line-height: 1.6;
    color: var(--gray-600);
    margin-bottom: 28px;
}

.article-meta-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 28px;
    padding: 24px 0;
    border-top: 1px solid var(--gray-200);
    border-bottom: 1px solid var(--gray-200);
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 12px;
}

.meta-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: var(--gray-100);
    border-radius: 12px;
    color: var(--primary-color);
}

.meta-content {
    display: flex;
    flex-direction: column;
}

.meta-label {
    font-size: 12px;
    color: var(--gray-500);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: 600;
}

.meta-value {
    font-size: 14px;
    color: var(--gray-800);
    font-weight: 500;
}

.article-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
    flex-wrap: wrap;
}

.action-group {
    display: flex;
    gap: 8px;
}

.action-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    background: var(--gray-100);
    border: none;
    border-radius: 12px;
    color: var(--gray-600);
    cursor: pointer;
    transition: var(--transition-fast);
    position: relative;
}

.action-btn:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

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

.action-btn.bookmarked:hover {
    background: var(--primary-dark);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    font-size: 14px;
    font-weight: 600;
    border-radius: 12px;
    border: none;
    cursor: pointer;
    transition: var(--transition-normal);
    text-decoration: none;
    position: relative;
    overflow: hidden;
}

.btn::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 5px;
    height: 5px;
    background: rgba(255, 255, 255, 0.5);
    opacity: 0;
    border-radius: 100%;
    transform: scale(1, 1) translate(-50%);
    transform-origin: 50% 50%;
}

.btn:focus:not(:active)::after {
    animation: ripple 1s ease-out;
}

@keyframes ripple {
    0% {
        transform: scale(0, 0);
        opacity: 0.5;
    }
    100% {
        transform: scale(20, 20);
        opacity: 0;
    }
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--gray-100);
    color: var(--gray-700);
    border: 1px solid var(--gray-200);
}

.btn-secondary:hover {
    background: var(--gray-200);
    transform: translateY(-2px);
}

.btn-outline {
    background: transparent;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

.btn-outline:hover {
    background: var(--primary-light);
}

.btn-sm {
    padding: 8px 16px;
    font-size: 13px;
}

.btn-block {
    display: flex;
    width: 100%;
}

/* Video Section */
.article-video-section {
    margin: 32px 0;
}

.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
    overflow: hidden;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

/* Article Content */
.article-content-section {
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 40px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
}

.content-wrapper {
    font-size: 18px;
    line-height: 1.8;
    color: var(--gray-700);
}

.content-wrapper h1,
.content-wrapper h2,
.content-wrapper h3,
.content-wrapper h4 {
    color: var(--gray-900);
    margin-top: 2em;
    margin-bottom: 1em;
    font-weight: 700;
    line-height: 1.3;
}

.content-wrapper h1 {
    font-size: 32px;
    border-bottom: 2px solid var(--gray-200);
    padding-bottom: 10px;
}

.content-wrapper h2 {
    font-size: 28px;
}

.content-wrapper h3 {
    font-size: 24px;
}

.content-wrapper h4 {
    font-size: 20px;
}

.content-wrapper p {
    margin-bottom: 1.5em;
}

.content-wrapper a {
    color: var(--primary-color);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: var(--transition-fast);
}

.content-wrapper a:hover {
    border-bottom-color: var(--primary-color);
}

.content-wrapper img {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius);
    margin: 2em 0;
    box-shadow: var(--shadow-md);
}

.content-wrapper blockquote {
    border-left: 4px solid var(--primary-color);
    padding: 1em 2em;
    margin: 2em 0;
    background: var(--gray-50);
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    font-style: italic;
    color: var(--gray-600);
}

.content-wrapper pre {
    background: var(--gray-900);
    color: var(--gray-100);
    padding: 1.5em;
    border-radius: var(--border-radius);
    overflow-x: auto;
    margin: 2em 0;
    font-size: 15px;
}

.content-wrapper code {
    background: var(--gray-100);
    padding: 0.2em 0.4em;
    border-radius: 4px;
    font-family: 'SF Mono', Monaco, 'Cascadia Mono', monospace;
    font-size: 0.9em;
}

.content-wrapper ul,
.content-wrapper ol {
    margin: 1.5em 0;
    padding-left: 2em;
}

.content-wrapper li {
    margin-bottom: 0.5em;
}

/* Questions Section */
.questions-section {
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 32px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
    flex-wrap: wrap;
    gap: 16px;
}

.section-title {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 24px;
    font-weight: 700;
    color: var(--gray-900);
}

.quiz-progress {
    display: flex;
    align-items: center;
    gap: 16px;
}

.progress-bar {
    width: 200px;
    height: 8px;
    background: var(--gray-200);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary-color);
    border-radius: 4px;
    transition: width 0.6s ease;
}

.progress-text {
    font-size: 14px;
    font-weight: 600;
    color: var(--gray-600);
    min-width: 120px;
}

.questions-grid {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.question-card {
    background: var(--gray-50);
    border-radius: var(--border-radius);
    padding: 24px;
    border: 1px solid var(--gray-200);
    transition: var(--transition-normal);
}

.question-card:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

.question-header {
    margin-bottom: 24px;
}

.question-tags {
    display: flex;
    gap: 8px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.question-number {
    background: var(--primary-color);
    color: white;
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 600;
}

.question-type {
    background: var(--gray-200);
    color: var(--gray-700);
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 14px;
    font-weight: 500;
}

.question-title {
    font-size: 18px;
    font-weight: 600;
    line-height: 1.5;
    color: var(--gray-900);
}

.question-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 24px;
}

.option-item {
    position: relative;
}

.option-input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
}

.option-label {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px;
    background: var(--light-color);
    border: 1px solid var(--gray-300);
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition-fast);
}

.option-label:hover {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.option-input:checked + .option-label {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.option-item.selected .option-label {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.option-item.correct .option-label {
    border-color: var(--success-color);
    background: rgba(46, 204, 113, 0.1);
    color: var(--success-color);
}

.option-item.incorrect .option-label {
    border-color: var(--danger-color);
    background: rgba(231, 76, 60, 0.1);
    color: var(--danger-color);
}

.option-marker {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--gray-200);
    color: var(--gray-700);
    border-radius: 8px;
    font-weight: 600;
    font-size: 14px;
    transition: var(--transition-fast);
}

.option-input:checked + .option-label .option-marker {
    background: var(--primary-color);
    color: white;
}

.option-item.selected .option-marker {
    background: var(--primary-color);
    color: white;
}

.option-item.correct .option-marker {
    background: var(--success-color);
    color: white;
}

.option-item.incorrect .option-marker {
    background: var(--danger-color);
    color: white;
}

.option-text {
    flex: 1;
    font-weight: 500;
}

.short-answer-container {
    margin-bottom: 24px;
}

.short-answer-input {
    width: 100%;
    padding: 16px;
    font-size: 16px;
    border: 1px solid var(--gray-300);
    border-radius: 12px;
    background: var(--light-color);
    transition: var(--transition-fast);
}

.short-answer-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.question-solution {
    background: var(--gray-50);
    border-radius: 12px;
    padding: 20px;
    margin-top: 24px;
    border: 1px solid var(--gray-200);
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.solution-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
    color: var(--success-color);
}

.solution-header h4 {
    font-size: 18px;
    font-weight: 600;
    color: var(--gray-900);
}

.solution-content {
    padding: 16px;
    background: var(--light-color);
    border-radius: 8px;
}

.correct-answer {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
    font-size: 16px;
}

.answer-value {
    background: var(--success-color);
    color: white;
    padding: 8px 16px;
    border-radius: 20px;
    font-weight: 600;
}

.explanation h5 {
    font-size: 16px;
    color: var(--gray-800);
    margin-bottom: 8px;
}

.explanation p {
    color: var(--gray-600);
    line-height: 1.6;
}

.question-actions {
    margin-top: 24px;
}

/* Tags Section */
.tags-section {
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 24px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
}

.tags-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 20px;
}

.tags-container {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.tag-item {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    background: var(--gray-100);
    color: var(--gray-700);
    border-radius: 20px;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    transition: var(--transition-fast);
    border: 1px solid transparent;
}

.tag-item:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    border-color: var(--primary-color);
}

/* Related Articles */
.related-articles-section {
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 32px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
}

.view-all-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    padding: 8px 16px;
    border-radius: 8px;
    transition: var(--transition-fast);
}

.view-all-link:hover {
    background: var(--primary-light);
    transform: translateX(4px);
}

.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
    margin-top: 24px;
}

.related-card {
    background: var(--gray-50);
    border-radius: var(--border-radius);
    overflow: hidden;
    transition: var(--transition-normal);
    border: 1px solid var(--gray-200);
}

.related-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.related-image {
    height: 180px;
    overflow: hidden;
}

.related-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.6s ease;
}

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

.related-content {
    padding: 20px;
}

.related-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
    font-size: 13px;
}

.related-category {
    background: var(--primary-light);
    color: var(--primary-color);
    padding: 4px 10px;
    border-radius: 12px;
    font-weight: 600;
}

.related-time {
    display: flex;
    align-items: center;
    gap: 4px;
    color: var(--gray-500);
}

.related-title {
    font-size: 18px;
    font-weight: 700;
    line-height: 1.4;
    color: var(--gray-900);
    margin-bottom: 12px;
}

.related-title a {
    color: inherit;
    text-decoration: none;
}

.related-title a:hover {
    color: var(--primary-color);
}

.related-excerpt {
    font-size: 14px;
    color: var(--gray-600);
    line-height: 1.6;
    margin-bottom: 16px;
}

.read-more-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    transition: var(--transition-fast);
}

.read-more-link:hover {
    gap: 12px;
    color: var(--primary-dark);
}

/* Comments Section */
.comments-section {
    background: var(--light-color);
    border-radius: var(--border-radius);
    padding: 32px;
    box-shadow: var(--shadow-md);
}

.comment-form-container {
    margin-bottom: 32px;
}

.comment-form {
    background: var(--gray-50);
    border-radius: var(--border-radius);
    padding: 24px;
}

.form-error {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 16px;
    background: rgba(231, 76, 60, 0.1);
    color: var(--danger-color);
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 14px;
}

.form-message {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 16px;
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 14px;
}

.form-message-success {
    background: rgba(46, 204, 113, 0.1);
    color: var(--success-color);
}

.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 8px;
}

.form-textarea {
    width: 100%;
    padding: 16px;
    font-size: 16px;
    line-height: 1.6;
    border: 1px solid var(--gray-300);
    border-radius: 12px;
    background: var(--light-color);
    transition: var(--transition-fast);
    resize: vertical;
    min-height: 120px;
}

.form-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.form-actions {
    display: flex;
    justify-content: flex-end;
}

.login-prompt {
    text-align: center;
    padding: 40px 20px;
    background: var(--gray-50);
    border-radius: var(--border-radius);
    margin-bottom: 32px;
}

.login-prompt h3 {
    font-size: 20px;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 12px;
}

.login-prompt p {
    color: var(--gray-600);
    margin-bottom: 24px;
}

.no-comments {
    text-align: center;
    padding: 60px 20px;
}

.no-comments h3 {
    font-size: 20px;
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 12px;
}

.no-comments p {
    color: var(--gray-500);
}

.comments-list {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.comment-item {
    display: flex;
    gap: 16px;
    padding: 24px;
    background: var(--gray-50);
    border-radius: var(--border-radius);
    border: 1px solid var(--gray-200);
}

.comment-avatar {
    flex-shrink: 0;
    width: 48px;
    height: 48px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 16px;
}

.comment-content {
    flex: 1;
}

.comment-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 12px;
    flex-wrap: wrap;
    gap: 12px;
}

.comment-author h4 {
    font-size: 16px;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 4px;
}

.comment-date {
    font-size: 13px;
    color: var(--gray-500);
}

.comment-body p {
    font-size: 15px;
    line-height: 1.6;
    color: var(--gray-700);
}

/* Sidebar */
.article-sidebar {
    display: flex;
    flex-direction: column;
    gap: 24px;
    position: sticky;
    top: 24px;
}

.sidebar-card {
    background: var(--light-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.card-header {
    padding: 20px;
    background: var(--gray-50);
    border-bottom: 1px solid var(--gray-200);
}

.card-title {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 18px;
    font-weight: 700;
    color: var(--gray-900);
}

.card-content {
    padding: 20px;
}

.author-info {
    display: flex;
    align-items: flex-start;
    gap: 16px;
}

.author-avatar {
    flex-shrink: 0;
    width: 56px;
    height: 56px;
    background: var(--primary-light);
    color: var(--primary-color);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.author-details h4 {
    font-size: 18px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 8px;
}

.author-bio {
    font-size: 14px;
    line-height: 1.5;
    color: var(--gray-600);
}

.popular-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.popular-item {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 12px;
    text-decoration: none;
    border-radius: 8px;
    transition: var(--transition-fast);
}

.popular-item:hover {
    background: var(--gray-100);
    transform: translateX(4px);
}

.popular-rank {
    flex-shrink: 0;
    width: 28px;
    height: 28px;
    background: var(--gray-200);
    color: var(--gray-700);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: 600;
}

.popular-item:nth-child(1) .popular-rank {
    background: #ff6b6b;
    color: white;
}

.popular-item:nth-child(2) .popular-rank {
    background: #4ecdc4;
    color: white;
}

.popular-item:nth-child(3) .popular-rank {
    background: #45b7d1;
    color: white;
}

.popular-content {
    flex: 1;
    min-width: 0;
}

.popular-content h4 {
    font-size: 14px;
    font-weight: 600;
    line-height: 1.4;
    color: var(--gray-800);
    margin-bottom: 4px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.popular-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 12px;
    color: var(--gray-500);
}

.newsletter-form .form-group {
    margin-bottom: 16px;
}

.form-input {
    width: 100%;
    padding: 12px 16px;
    font-size: 14px;
    border: 1px solid var(--gray-300);
    border-radius: 8px;
    background: var(--light-color);
    transition: var(--transition-fast);
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

/* Tooltips */
.tooltip {
    position: fixed;
    background: var(--gray-900);
    color: white;
    padding: 8px 12px;
    border-radius: 6px;
    font-size: 12px;
    font-weight: 500;
    z-index: 1000;
    pointer-events: none;
    white-space: nowrap;
    transform: translateY(-5px);
    opacity: 0;
    animation: tooltipFadeIn 0.2s ease forwards;
}

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

.tooltip::after {
    content: '';
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    border: 5px solid transparent;
    border-top-color: var(--gray-900);
}

/* ===                      === */
/* === Articles Page        === */
/* ===                      === */

.articles-page-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px 60px;
}

/* Breadcrumb */
.breadcrumb-nav {
    padding: 24px 0 16px;
}

.breadcrumb-list {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    list-style: none;
    padding: 0;
    margin: 0;
}

.breadcrumb-item {
    display: flex;
    align-items: center;
    gap: 8px;
}

.breadcrumb-link {
    color: var(--gray-600);
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    transition: var(--transition-fast);
    padding: 4px 8px;
    border-radius: var(--border-radius-sm);
}

.breadcrumb-link:hover {
    color: var(--primary-color);
    background: var(--primary-light);
}

.breadcrumb-current {
    color: var(--gray-800);
    font-weight: 600;
    font-size: 14px;
}

/* Main Grid */
.articles-main-grid {
    display: grid;
    grid-template-columns: 1fr 360px;
    gap: 32px;
    padding: 24px 0 48px;
}

@media (max-width: 1024px) {
    .articles-main-grid {
        grid-template-columns: 1fr;
        gap: 24px;
    }
}

/* Header */
.articles-header {
    background: var(--light-color);
    border-radius: var(--border-radius-lg);
    padding: 32px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-md);
}

.header-content {
    margin-bottom: 24px;
}

.articles-main-title {
    font-size: 36px;
    font-weight: 800;
    color: var(--dark-color);
    line-height: 1.2;
    margin-bottom: 12px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.articles-subtitle {
    font-size: 18px;
    color: var(--gray-600);
    max-width: 600px;
}

.articles-stats {
    display: flex;
    gap: 24px;
    padding-top: 24px;
    border-top: 1px solid var(--gray-200);
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--gray-600);
    font-size: 14px;
    font-weight: 500;
}

/* Articles Grid */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 24px;
    margin-bottom: 48px;
}

@media (max-width: 768px) {
    .articles-grid {
        grid-template-columns: 1fr;
    }
}

/* Article Card */
.article-card {
    background: var(--light-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: var(--transition-normal);
    position: relative;
    height: 100%;
    display: flex;
    flex-direction: column;
}

.article-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.article-image {
    position: relative;
    height: 200px;
    overflow: hidden;
}

.article-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.6s ease;
}

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

.article-image-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(to bottom, transparent 50%, rgba(0,0,0,0.3));
}

.article-content {
    padding: 24px;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.article-header {
    margin-bottom: 20px;
}

.article-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 16px;
}

.tag {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.tag-level {
    background: var(--primary-light);
    color: var(--primary-color);
}

.tag-easy {
    background: rgba(46, 204, 113, 0.1);
    color: var(--success-color);
}

.tag-medium {
    background: rgba(243, 156, 18, 0.1);
    color: var(--warning-color);
}

.tag-hard {
    background: rgba(231, 76, 60, 0.1);
    color: var(--danger-color);
}

.tag-questions {
    background: rgba(114, 9, 183, 0.1);
    color: var(--secondary-color);
}

.article-title {
    font-size: 20px;
    font-weight: 700;
    color: var(--dark-color);
    line-height: 1.4;
    margin-bottom: 12px;
}

.article-title-link {
    color: inherit;
    text-decoration: none;
    transition: var(--transition-fast);
}

.article-title-link:hover {
    color: var(--primary-color);
}

.article-excerpt {
    color: var(--gray-600);
    font-size: 15px;
    line-height: 1.6;
    margin-bottom: 20px;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.article-footer {
    margin-top: auto;
    padding-top: 20px;
    border-top: 1px solid var(--gray-200);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
}

.article-meta {
    display: flex;
    gap: 16px;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--gray-500);
    font-size: 13px;
    font-weight: 500;
}

.article-date {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--gray-500);
    font-size: 13px;
    font-weight: 500;
    margin-left: auto;
}

.article-read-more {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    padding: 8px 16px;
    border-radius: var(--border-radius-sm);
    background: var(--primary-light);
    transition: var(--transition-normal);
    white-space: nowrap;
}

.article-read-more:hover {
    background: var(--primary-color);
    color: white;
    transform: translateX(4px);
}

/* Empty State */
.articles-empty-state {
    background: var(--light-color);
    border-radius: var(--border-radius-lg);
    padding: 64px 32px;
    text-align: center;
    box-shadow: var(--shadow-md);
}

.empty-state-icon {
    color: var(--gray-300);
    margin-bottom: 24px;
}

.empty-state-title {
    font-size: 24px;
    font-weight: 700;
    color: var(--gray-800);
    margin-bottom: 12px;
}

.empty-state-description {
    color: var(--gray-600);
    max-width: 400px;
    margin: 0 auto 32px;
    font-size: 16px;
    line-height: 1.6;
}

.empty-state-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
}

/* Pagination */
.articles-pagination {
    margin-top: 48px;
}

.pagination-list {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    list-style: none;
    padding: 0;
    margin: 0;
}

.pagination-item {
    display: inline-flex;
}

.pagination-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 16px;
    border-radius: var(--border-radius-sm);
    color: var(--gray-600);
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    transition: var(--transition-fast);
    min-width: 44px;
    height: 44px;
    border: 1px solid transparent;
}

.pagination-link:hover {
    background: var(--primary-light);
    color: var(--primary-color);
    border-color: var(--primary-light);
}

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

.pagination-prev,
.pagination-next {
    gap: 8px;
    padding: 10px 20px;
}

.pagination-ellipsis {
    color: var(--gray-400);
    padding: 10px 8px;
    user-select: none;
}

.pagination-numbers {
    display: flex;
    gap: 4px;
}

/* Sidebar Widgets */
.articles-sidebar {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

@media (max-width: 1024px) {
    .articles-sidebar {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 24px;
    }
}

@media (max-width: 640px) {
    .articles-sidebar {
        grid-template-columns: 1fr;
    }
}

.sidebar-widget {
    background: var(--light-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.widget-header {
    padding: 20px 24px;
    background: var(--primary-light);
    border-bottom: 1px solid var(--gray-200);
}

.widget-title {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 18px;
    font-weight: 700;
    color: var(--dark-color);
    margin: 0;
}

.widget-content {
    padding: 24px;
}

/* Categories */
.categories-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.category-item {
    border-bottom: 1px solid var(--gray-200);
}

.category-item:last-child {
    border-bottom: none;
}

.category-link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 0;
    color: var(--gray-700);
    text-decoration: none;
    transition: var(--transition-fast);
}

.category-link:hover {
    color: var(--primary-color);
}

.category-link.active {
    color: var(--primary-color);
    font-weight: 600;
}

.category-link.active .category-count {
    background: var(--primary-color);
    color: white;
}

.category-name {
    flex: 1;
}

.category-count {
    background: var(--gray-100);
    color: var(--gray-600);
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    min-width: 32px;
    text-align: center;
    transition: var(--transition-fast);
}

/* Popular Articles */
.popular-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.popular-item {
    border-bottom: 1px solid var(--gray-200);
}

.popular-item:last-child {
    border-bottom: none;
}

.popular-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 0;
    text-decoration: none;
    transition: var(--transition-fast);
}

.popular-link:hover {
    transform: translateX(4px);
}

.popular-rank {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    background: var(--primary-light);
    color: var(--primary-color);
    border-radius: 50%;
    font-size: 14px;
    font-weight: 700;
    flex-shrink: 0;
}

.popular-content {
    flex: 1;
    min-width: 0;
}

.popular-title {
    font-size: 15px;
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 4px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.popular-meta {
    display: flex;
    align-items: center;
    gap: 8px;
}

.popular-views {
    display: flex;
    align-items: center;
    gap: 4px;
    color: var(--gray-500);
    font-size: 12px;
    font-weight: 500;
}

/* CTA Widget */
.cta-widget {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
}

.cta-content {
    padding: 32px 24px;
    text-align: center;
}

.cta-title {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 8px;
}

.cta-text {
    font-size: 14px;
    opacity: 0.9;
    margin-bottom: 24px;
}

/* Responsive Design */
@media (max-width: 1200px) {
    .article-sidebar {
        position: static;
    }
}

@media (max-width: 992px) {
    .article-detail-container,
    .articles-page-container {
        padding: 0 16px 40px;
    }
    
    .article-title {
        font-size: 32px;
    }
    
    .article-excerpt {
        font-size: 16px;
    }
    
    .content-wrapper {
        font-size: 16px;
    }
    
    .content-wrapper h1 {
        font-size: 28px;
    }
    
    .content-wrapper h2 {
        font-size: 24px;
    }
    
    .content-wrapper h3 {
        font-size: 20px;
    }
    
    .content-wrapper h4 {
        font-size: 18px;
    }
    
    .section-title {
        font-size: 20px;
    }
    
    .articles-main-title {
        font-size: 32px;
    }
    
    .articles-subtitle {
        font-size: 16px;
    }
}

@media (max-width: 768px) {
    .article-header-content {
        padding: 24px;
    }
    
    .article-title {
        font-size: 28px;
    }
    
    .article-hero-image {
        height: 300px;
    }
    
    .article-meta-grid {
        grid-template-columns: 1fr;
    }
    
    .article-actions {
        flex-direction: column;
        align-items: stretch;
    }
    
    .action-group {
        justify-content: center;
    }
    
    .section-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .quiz-progress {
        width: 100%;
    }
    
    .related-grid {
        grid-template-columns: 1fr;
    }
    
    .comment-item {
        flex-direction: column;
    }
    
    .articles-header {
        padding: 24px;
    }
    
    .articles-main-title {
        font-size: 28px;
    }
    
    .articles-subtitle {
        font-size: 16px;
    }
    
    .articles-stats {
        flex-direction: column;
        gap: 12px;
    }
    
    .article-content {
        padding: 20px;
    }
    
    .article-footer {
        flex-wrap: wrap;
    }
    
    .article-date {
        margin-left: 0;
    }
}

@media (max-width: 576px) {
    .article-title {
        font-size: 24px;
    }
    
    .article-header-content,
    .article-content-section,
    .questions-section,
    .related-articles-section,
    .comments-section {
        padding: 20px;
    }
    
    .article-meta-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .question-title {
        font-size: 16px;
    }
    
    .option-label {
        padding: 12px;
    }
    
    .btn {
        width: 100%;
        justify-content: center;
    }
    
    .articles-main-title {
        font-size: 24px;
    }
    
    .articles-grid {
        gap: 16px;
    }
    
    .article-image {
        height: 160px;
    }
    
    .article-title {
        font-size: 18px;
    }
    
    .article-footer {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }
    
    .article-meta {
        width: 100%;
        justify-content: space-between;
    }
    
    .article-date {
        order: -1;
        width: 100%;
        justify-content: flex-start;
    }
    
    .article-read-more {
        width: 100%;
        justify-content: center;
    }
    
    .pagination-list {
        flex-wrap: wrap;
    }
    
    .pagination-prev,
    .pagination-next {
        width: 100%;
        justify-content: center;
    }
    
    .pagination-numbers {
        order: -1;
        width: 100%;
        justify-content: center;
    }
}

/* Print Styles */
@media print {
    .article-breadcrumb,
    .article-actions,
    .article-sidebar,
    .comments-section,
    .questions-section .question-actions,
    .view-all-link,
    .show-solution-btn,
    .articles-sidebar,
    .breadcrumb-nav,
    .articles-empty-state .empty-state-actions,
    .article-read-more,
    .pagination-list {
        display: none !important;
    }
    
    .article-layout {
        display: block;
    }
    
    .article-header-section,
    .article-content-section {
        box-shadow: none;
        border: none;
    }
    
    .article-title {
        color: black;
        font-size: 24pt;
    }
    
    .content-wrapper {
        font-size: 12pt;
        line-height: 1.6;
    }
    
    .article-content-section {
        page-break-inside: avoid;
    }
    
    a {
        color: black !important;
        text-decoration: underline !important;
    }
    
    .related-card {
        page-break-inside: avoid;
    }
    
    .articles-main-grid {
        grid-template-columns: 1fr;
        gap: 0;
    }
    
    .article-card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ddd;
        margin-bottom: 20px;
    }
    
    .articles-header {
        box-shadow: none;
        border: 1px solid #ddd;
    }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* Focus Styles */
:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Skip to content link */
.skip-to-content {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: white;
    padding: 8px 16px;
    text-decoration: none;
    border-radius: 0 0 4px 0;
    z-index: 1001;
}

.skip-to-content:focus {
    top: 0;
}

/* Animation */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.article-card {
    animation: fadeIn 0.5s ease-out;
}