/* ========================================
   Fizika Portali - Main Stylesheet
   ======================================== */

/* CSS Variables - Dark Modern Theme */
:root {
    --color-primary: #0a0e1a;
    --color-primary-light: #111827;
    --color-secondary: #3b82f6;
    --color-secondary-light: #60a5fa;
    --color-accent: #22d3ee;
    --color-accent-warm: #f97316;
    --color-background: #030712;
    --color-background-alt: #0f172a;
    --color-surface: #1e293b;
    --color-surface-dark: #334155;
    --color-surface-light: #475569;
    --color-text: #f1f5f9;
    --color-text-muted: #94a3b8;
    --color-text-light: #64748b;
    --color-border: #334155;
    --color-border-light: #475569;
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 50%, #ec4899 100%);
    --gradient-hero: linear-gradient(135deg, #0f172a 0%, #1e3a5f 50%, #0f172a 100%);
    --gradient-card: linear-gradient(145deg, rgba(30, 41, 59, 0.8) 0%, rgba(15, 23, 42, 0.9) 100%);
    --gradient-glow: radial-gradient(ellipse at center, rgba(59, 130, 246, 0.15) 0%, transparent 70%);

    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;

    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 0.75rem;
    --spacing-4: 1rem;
    --spacing-5: 1.25rem;
    --spacing-6: 1.5rem;
    --spacing-8: 2rem;
    --spacing-10: 2.5rem;
    --spacing-12: 3rem;
    --spacing-16: 4rem;
    --spacing-20: 5rem;
    --spacing-24: 6rem;

    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;

    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-background);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background-image:
        radial-gradient(ellipse at top, rgba(59, 130, 246, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at bottom right, rgba(139, 92, 246, 0.05) 0%, transparent 50%);
    background-attachment: fixed;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color var(--transition-fast);
}

ul, ol {
    list-style: none;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

/* Container */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-4);
}

@media (min-width: 768px) {
    .container {
        padding: 0 var(--spacing-6);
    }
}

/* ========================================
   Header
   ======================================== */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: rgba(3, 7, 18, 0.85);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text);
}

.logo-icon {
    width: 36px;
    height: 36px;
    color: var(--color-secondary);
    filter: drop-shadow(0 0 8px rgba(59, 130, 246, 0.5));
}

/* Navigation */
.nav {
    display: none;
}

@media (min-width: 1024px) {
    .nav {
        display: block;
    }
}

.nav-list {
    display: flex;
    align-items: center;
    gap: var(--spacing-1);
}

.nav-link {
    display: block;
    padding: var(--spacing-2) var(--spacing-4);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-text-muted);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
    position: relative;
}

.nav-link:hover {
    color: var(--color-text);
    background-color: var(--color-surface);
}

.nav-link.active {
    color: var(--color-secondary);
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.15) 0%, rgba(139, 92, 246, 0.1) 100%);
}

/* Dropdown */
.nav-dropdown {
    position: relative;
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    min-width: 220px;
    padding: var(--spacing-2);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4), 0 0 60px rgba(59, 130, 246, 0.1);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all var(--transition-fast);
    backdrop-filter: blur(20px);
}

.nav-dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-menu a {
    display: block;
    padding: var(--spacing-2) var(--spacing-3);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.dropdown-menu a:hover {
    color: var(--color-text);
    background-color: var(--color-surface);
}

/* Mobile Menu Button */
.mobile-menu-btn {
    display: flex;
    flex-direction: column;
    gap: 5px;
    padding: var(--spacing-2);
}

@media (min-width: 1024px) {
    .mobile-menu-btn {
        display: none;
    }
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-text);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

.mobile-menu-btn.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.mobile-menu-btn.active span:nth-child(2) {
    opacity: 0;
}

.mobile-menu-btn.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* Mobile Navigation */
.mobile-nav {
    position: fixed;
    top: 72px;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(180deg, var(--color-background) 0%, var(--color-primary-light) 100%);
    padding: var(--spacing-4);
    transform: translateX(-100%);
    transition: transform var(--transition-normal);
    z-index: 99;
    overflow-y: auto;
    backdrop-filter: blur(20px);
}

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

@media (min-width: 1024px) {
    .mobile-nav {
        display: none;
    }
}

.mobile-nav-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-1);
}

.mobile-nav-list a {
    display: block;
    padding: var(--spacing-3) var(--spacing-4);
    font-size: var(--font-size-lg);
    font-weight: 500;
    color: var(--color-text);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.mobile-nav-list a:hover {
    background-color: var(--color-surface);
    color: var(--color-secondary);
}

/* ========================================
   Main Content
   ======================================== */
.main {
    flex: 1;
}

/* ========================================
   Hero Section
   ======================================== */
.hero {
    position: relative;
    padding: var(--spacing-20) 0;
    background: linear-gradient(135deg, #0a0e1a 0%, #1e3a5f 40%, #0f172a 70%, #0a0e1a 100%);
    color: white;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background:
        radial-gradient(ellipse at 20% 30%, rgba(59, 130, 246, 0.3) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 70%, rgba(139, 92, 246, 0.2) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 100%, rgba(34, 211, 238, 0.15) 0%, transparent 40%);
    animation: heroGlow 8s ease-in-out infinite alternate;
}

@keyframes heroGlow {
    0% { opacity: 0.7; }
    100% { opacity: 1; }
}

.hero::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.03'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    opacity: 0.5;
}

@media (min-width: 768px) {
    .hero {
        padding: var(--spacing-24) 0;
    }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 720px;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-2);
    padding: var(--spacing-2) var(--spacing-5);
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.2) 0%, rgba(139, 92, 246, 0.2) 100%);
    border: 1px solid rgba(59, 130, 246, 0.3);
    border-radius: var(--radius-full);
    font-size: var(--font-size-sm);
    font-weight: 500;
    margin-bottom: var(--spacing-6);
    backdrop-filter: blur(8px);
    animation: badgePulse 2s ease-in-out infinite;
}

@keyframes badgePulse {
    0%, 100% { box-shadow: 0 0 20px rgba(59, 130, 246, 0.3); }
    50% { box-shadow: 0 0 30px rgba(59, 130, 246, 0.5); }
}

.hero-badge svg {
    width: 16px;
    height: 16px;
}

.hero-title {
    font-size: var(--font-size-3xl);
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: var(--spacing-5);
    text-wrap: balance;
    background: linear-gradient(135deg, #ffffff 0%, #94a3b8 50%, #ffffff 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

@media (min-width: 768px) {
    .hero-title {
        font-size: var(--font-size-5xl);
    }
}

.hero-desc {
    font-size: var(--font-size-lg);
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: var(--spacing-8);
    line-height: 1.7;
    text-wrap: pretty;
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-4);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    padding: var(--spacing-3) var(--spacing-6);
    font-size: var(--font-size-sm);
    font-weight: 600;
    border-radius: var(--radius-xl);
    transition: all var(--transition-normal);
    white-space: nowrap;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
    transition: left 0.5s ease;
}

.btn:hover::before {
    left: 100%;
}

.btn-primary {
    background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
    color: white;
    box-shadow: 0 4px 20px rgba(59, 130, 246, 0.4);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 30px rgba(59, 130, 246, 0.5);
}

.btn-outline {
    background-color: transparent;
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.3);
    backdrop-filter: blur(4px);
}

.btn-outline:hover {
    background-color: rgba(255, 255, 255, 0.1);
    border-color: var(--color-secondary);
    box-shadow: 0 0 20px rgba(59, 130, 246, 0.3);
}

.btn-secondary {
    background: linear-gradient(135deg, var(--color-surface) 0%, var(--color-surface-dark) 100%);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    border-color: var(--color-secondary);
    box-shadow: 0 4px 20px rgba(59, 130, 246, 0.2);
}

.btn svg {
    width: 18px;
    height: 18px;
}

/* ========================================
   Stats Section
   ======================================== */
.stats {
    padding: var(--spacing-12) 0;
    background: linear-gradient(180deg, var(--color-primary-light) 0%, var(--color-background) 100%);
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-6);
}

@media (min-width: 768px) {
    .stats-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

.stat-item {
    text-align: center;
    padding: var(--spacing-6);
    background: linear-gradient(145deg, rgba(30, 41, 59, 0.5) 0%, rgba(15, 23, 42, 0.8) 100%);
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-border);
    transition: all var(--transition-normal);
}

.stat-item:hover {
    border-color: var(--color-secondary);
    transform: translateY(-4px);
    box-shadow: 0 10px 30px rgba(59, 130, 246, 0.2);
}

.stat-number {
    font-size: var(--font-size-3xl);
    font-weight: 800;
    background: linear-gradient(135deg, var(--color-secondary) 0%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-1);
}

@media (min-width: 768px) {
    .stat-number {
        font-size: var(--font-size-4xl);
    }
}

.stat-label {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* ========================================
   Section Styles
   ======================================== */
.section {
    padding: var(--spacing-16) 0;
}

@media (min-width: 768px) {
    .section {
        padding: var(--spacing-20) 0;
    }
}

.section-header {
    text-align: center;
    max-width: 640px;
    margin: 0 auto var(--spacing-12);
}

.section-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--spacing-3);
    position: relative;
    display: inline-block;
}

.section-header .section-title::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background: linear-gradient(90deg, var(--color-secondary) 0%, var(--color-accent) 100%);
    border-radius: var(--radius-full);
}

@media (min-width: 768px) {
    .section-title {
        font-size: var(--font-size-3xl);
    }
}

.section-desc {
    font-size: var(--font-size-lg);
    color: var(--color-text-muted);
    line-height: 1.7;
}

/* ========================================
   Cards
   ======================================== */
.card-grid {
    display: grid;
    gap: var(--spacing-6);
}

.card-grid-2 {
    grid-template-columns: 1fr;
}

@media (min-width: 768px) {
    .card-grid-2 {
        grid-template-columns: repeat(2, 1fr);
    }
}

.card-grid-3 {
    grid-template-columns: 1fr;
}

@media (min-width: 640px) {
    .card-grid-3 {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1024px) {
    .card-grid-3 {
        grid-template-columns: repeat(3, 1fr);
    }
}

.card-grid-4 {
    grid-template-columns: repeat(2, 1fr);
}

@media (min-width: 768px) {
    .card-grid-4 {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (min-width: 1024px) {
    .card-grid-4 {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* Card */
.card {
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    transition: all var(--transition-normal);
    position: relative;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--color-secondary) 0%, var(--color-accent) 50%, transparent 100%);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.card:hover {
    border-color: var(--color-secondary);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4), 0 0 60px rgba(59, 130, 246, 0.1);
    transform: translateY(-8px);
}

.card:hover::before {
    opacity: 1;
}

.card-image {
    position: relative;
    aspect-ratio: 16 / 10;
    overflow: hidden;
    background-color: var(--color-surface);
}

.card-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

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

.card-badge {
    position: absolute;
    top: var(--spacing-3);
    left: var(--spacing-3);
    padding: var(--spacing-1) var(--spacing-3);
    background: linear-gradient(135deg, var(--color-secondary) 0%, rgba(139, 92, 246, 0.9) 100%);
    color: white;
    font-size: var(--font-size-xs);
    font-weight: 600;
    border-radius: var(--radius-full);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
    backdrop-filter: blur(4px);
}

.card-content {
    padding: var(--spacing-5);
}

.card-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-2);
}

.card-meta svg {
    width: 14px;
    height: 14px;
}

.card-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-2);
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.card-desc {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    line-height: 1.6;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
    margin-bottom: var(--spacing-4);
}

.card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--spacing-4);
    border-top: 1px solid var(--color-border);
}

.card-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-2);
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-secondary);
}

.card-link svg {
    width: 16px;
    height: 16px;
    transition: transform var(--transition-fast);
}

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

/* Feature Card */
.feature-card {
    padding: var(--spacing-6);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-2xl);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(ellipse at top left, rgba(59, 130, 246, 0.1) 0%, transparent 50%);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.feature-card:hover {
    border-color: var(--color-secondary);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3), 0 0 40px rgba(59, 130, 246, 0.15);
    transform: translateY(-6px);
}

.feature-card:hover::before {
    opacity: 1;
}

.feature-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.2) 0%, rgba(139, 92, 246, 0.2) 100%);
    border: 1px solid rgba(59, 130, 246, 0.3);
    border-radius: var(--radius-xl);
    margin-bottom: var(--spacing-4);
    color: var(--color-secondary);
    position: relative;
    z-index: 1;
}

.feature-icon svg {
    width: 24px;
    height: 24px;
}

.feature-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-2);
}

.feature-desc {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    line-height: 1.6;
}

/* ========================================
   Page Header
   ======================================== */
.page-header {
    padding: var(--spacing-12) 0;
    background: linear-gradient(180deg, var(--color-primary-light) 0%, var(--color-background) 100%);
    border-bottom: 1px solid var(--color-border);
    position: relative;
    overflow: hidden;
}

.page-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(ellipse at 30% 50%, rgba(59, 130, 246, 0.1) 0%, transparent 50%);
}

@media (min-width: 768px) {
    .page-header {
        padding: var(--spacing-16) 0;
    }
}

.page-header-content {
    max-width: 640px;
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-4);
}

.breadcrumb a:hover {
    color: var(--color-secondary);
}

.breadcrumb svg {
    width: 16px;
    height: 16px;
}

.page-title {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--spacing-3);
}

@media (min-width: 768px) {
    .page-title {
        font-size: var(--font-size-4xl);
    }
}

.page-desc {
    font-size: var(--font-size-lg);
    color: var(--color-text-muted);
    line-height: 1.7;
}

/* ========================================
   Content Styles
   ======================================== */
.content {
    padding: var(--spacing-12) 0;
}

.content-grid {
    display: grid;
    gap: var(--spacing-8);
}

@media (min-width: 1024px) {
    .content-grid {
        grid-template-columns: 280px 1fr;
    }
}

/* Sidebar */
.sidebar {
    display: none;
}

@media (min-width: 1024px) {
    .sidebar {
        display: block;
    }
}

.sidebar-section {
    margin-bottom: var(--spacing-6);
}

.sidebar-title {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-3);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.sidebar-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-1);
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    padding: var(--spacing-3) var(--spacing-4);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
    border: 1px solid transparent;
}

.sidebar-link:hover {
    color: var(--color-text);
    background: linear-gradient(145deg, rgba(30, 41, 59, 0.5) 0%, rgba(15, 23, 42, 0.5) 100%);
    border-color: var(--color-border);
}

.sidebar-link.active {
    color: var(--color-secondary);
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.15) 0%, rgba(139, 92, 246, 0.1) 100%);
    border-color: rgba(59, 130, 246, 0.3);
}

.sidebar-link svg {
    width: 18px;
    height: 18px;
}

/* Article Content */
.article {
    max-width: 720px;
}

.article-header {
    margin-bottom: var(--spacing-8);
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--spacing-4);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-4);
}

.article-meta svg {
    width: 16px;
    height: 16px;
}

.article-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-text);
    line-height: 1.3;
}

@media (min-width: 768px) {
    .article-title {
        font-size: var(--font-size-3xl);
    }
}

.article-image {
    margin-bottom: var(--spacing-8);
    border-radius: var(--radius-xl);
    overflow: hidden;
}

.article-image img {
    width: 100%;
}

.article-body {
    font-size: var(--font-size-base);
    line-height: 1.8;
    color: var(--color-text);
}

.article-body h2 {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin: var(--spacing-8) 0 var(--spacing-4);
}

.article-body h3 {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin: var(--spacing-6) 0 var(--spacing-3);
}

.article-body p {
    margin-bottom: var(--spacing-4);
}

.article-body ul, .article-body ol {
    margin: var(--spacing-4) 0;
    padding-left: var(--spacing-6);
}

.article-body ul {
    list-style: disc;
}

.article-body ol {
    list-style: decimal;
}

.article-body li {
    margin-bottom: var(--spacing-2);
}

.article-body blockquote {
    margin: var(--spacing-6) 0;
    padding: var(--spacing-4) var(--spacing-6);
    background-color: var(--color-surface);
    border-left: 4px solid var(--color-secondary);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    font-style: italic;
    color: var(--color-text-muted);
}

.article-body pre {
    margin: var(--spacing-6) 0;
    padding: var(--spacing-4);
    background-color: var(--color-primary);
    border-radius: var(--radius-lg);
    overflow-x: auto;
    color: white;
    font-family: monospace;
    font-size: var(--font-size-sm);
}

.article-body code {
    padding: var(--spacing-1) var(--spacing-2);
    background-color: var(--color-surface);
    border-radius: var(--radius-sm);
    font-family: monospace;
    font-size: var(--font-size-sm);
}

.article-body img {
    margin: var(--spacing-6) 0;
    border-radius: var(--radius-lg);
}

/* Download Box */
.download-box {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-4);
    padding: var(--spacing-5) var(--spacing-6);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    margin: var(--spacing-6) 0;
    transition: all var(--transition-normal);
}

.download-box:hover {
    border-color: var(--color-secondary);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.download-info {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
}

.download-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-secondary) 0%, rgba(139, 92, 246, 0.8) 100%);
    color: white;
    border-radius: var(--radius-lg);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
}

.download-icon svg {
    width: 20px;
    height: 20px;
}

.download-name {
    font-weight: 600;
    color: var(--color-text);
}

.download-size {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* ========================================
   Test Page Styles
   ======================================== */
.test-container {
    max-width: 800px;
    margin: 0 auto;
}

.test-header {
    text-align: center;
    margin-bottom: var(--spacing-8);
}

.test-progress {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    margin-bottom: var(--spacing-6);
}

.test-progress-bar {
    flex: 1;
    height: 8px;
    background-color: var(--color-surface-dark);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.test-progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-secondary) 0%, var(--color-accent) 100%);
    border-radius: var(--radius-full);
    transition: width var(--transition-normal);
    box-shadow: 0 0 10px rgba(59, 130, 246, 0.5);
}

.test-progress-text {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-text-muted);
    white-space: nowrap;
}

.question-card {
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-2xl);
    padding: var(--spacing-8);
    margin-bottom: var(--spacing-6);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.question-number {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--color-secondary);
    margin-bottom: var(--spacing-3);
}

.question-text {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-4);
    line-height: 1.5;
}

.question-image {
    margin-bottom: var(--spacing-4);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.question-image img {
    width: 100%;
}

.answers-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-3);
}

.answer-option {
    position: relative;
}

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

.answer-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-3);
    padding: var(--spacing-4);
    background: linear-gradient(145deg, rgba(30, 41, 59, 0.5) 0%, rgba(15, 23, 42, 0.8) 100%);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-xl);
    cursor: pointer;
    transition: all var(--transition-normal);
}

.answer-label:hover {
    border-color: var(--color-secondary);
    background: linear-gradient(145deg, rgba(59, 130, 246, 0.1) 0%, rgba(15, 23, 42, 0.8) 100%);
    transform: translateX(4px);
}

.answer-option input:checked + .answer-label {
    background: linear-gradient(145deg, rgba(59, 130, 246, 0.2) 0%, rgba(139, 92, 246, 0.1) 100%);
    border-color: var(--color-secondary);
    box-shadow: 0 0 20px rgba(59, 130, 246, 0.2);
}

.answer-radio {
    width: 20px;
    height: 20px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: all var(--transition-fast);
}

.answer-option input:checked + .answer-label .answer-radio {
    border-color: var(--color-secondary);
}

.answer-option input:checked + .answer-label .answer-radio::after {
    content: '';
    width: 10px;
    height: 10px;
    background-color: var(--color-secondary);
    border-radius: var(--radius-full);
}

.answer-text {
    font-size: var(--font-size-base);
    color: var(--color-text);
}

.answer-image {
    width: 60px;
    height: 60px;
    object-fit: cover;
    border-radius: var(--radius-md);
}

/* Test Result */
.answer-option.correct .answer-label {
    background-color: rgba(16, 185, 129, 0.1);
    border-color: var(--color-success);
}

.answer-option.incorrect .answer-label {
    background-color: rgba(239, 68, 68, 0.1);
    border-color: var(--color-error);
}

.test-actions {
    display: flex;
    justify-content: space-between;
    gap: var(--spacing-4);
    margin-top: var(--spacing-8);
}

.test-result {
    text-align: center;
    padding: var(--spacing-12);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border-radius: var(--radius-2xl);
    border: 1px solid var(--color-border);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.3);
}

.result-score {
    font-size: var(--font-size-5xl);
    font-weight: 800;
    background: linear-gradient(135deg, var(--color-secondary) 0%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-4);
}

.result-text {
    font-size: var(--font-size-lg);
    color: var(--color-text-muted);
}

/* Level Badges */
.level-badge {
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-1) var(--spacing-3);
    font-size: var(--font-size-xs);
    font-weight: 600;
    border-radius: var(--radius-full);
}

.level-badge.easy {
    background-color: rgba(16, 185, 129, 0.1);
    color: var(--color-success);
}

.level-badge.medium {
    background-color: rgba(245, 158, 11, 0.1);
    color: var(--color-warning);
}

.level-badge.high {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--color-error);
}

/* ========================================
   Video Player
   ======================================== */
.video-container {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
    border-radius: var(--radius-xl);
    background-color: var(--color-primary);
}

.video-container iframe,
.video-container video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

/* ========================================
   Book Card
   ======================================== */
.book-card {
    display: flex;
    gap: var(--spacing-4);
    padding: var(--spacing-4);
    background-color: var(--color-background);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    transition: all var(--transition-normal);
}

.book-card:hover {
    border-color: var(--color-secondary);
    box-shadow: var(--shadow-md);
}

.book-cover {
    width: 120px;
    flex-shrink: 0;
    aspect-ratio: 3 / 4;
    border-radius: var(--radius-lg);
    overflow: hidden;
    background-color: var(--color-surface);
}

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

.book-info {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.book-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-1);
}

.book-author {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-3);
}

.book-desc {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    line-height: 1.6;
    flex: 1;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* ========================================
   News Card
   ======================================== */
.news-card {
    display: flex;
    flex-direction: column;
}

@media (min-width: 768px) {
    .news-card.featured {
        flex-direction: row;
        gap: var(--spacing-6);
    }

    .news-card.featured .card-image {
        flex: 1;
        aspect-ratio: 16 / 12;
    }

    .news-card.featured .card-content {
        flex: 1;
        display: flex;
        flex-direction: column;
        justify-content: center;
    }
}

/* ========================================
   Filter & Search
   ======================================== */
.filter-bar {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--spacing-4);
    padding: var(--spacing-5);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-2xl);
    margin-bottom: var(--spacing-8);
}

.search-box {
    flex: 1;
    min-width: 200px;
    position: relative;
}

.search-box input {
    width: 100%;
    padding: var(--spacing-3) var(--spacing-4);
    padding-left: var(--spacing-10);
    font-size: var(--font-size-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    background-color: var(--color-background-alt);
    color: var(--color-text);
    transition: all var(--transition-fast);
}

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

.search-box input:focus {
    outline: none;
    border-color: var(--color-secondary);
    box-shadow: 0 0 20px rgba(59, 130, 246, 0.2);
    background-color: var(--color-primary-light);
}

.search-box svg {
    position: absolute;
    left: var(--spacing-3);
    top: 50%;
    transform: translateY(-50%);
    width: 18px;
    height: 18px;
    color: var(--color-text-muted);
}

.filter-select {
    padding: var(--spacing-3) var(--spacing-4);
    font-size: var(--font-size-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    background-color: var(--color-background-alt);
    color: var(--color-text);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.filter-select:focus {
    outline: none;
    border-color: var(--color-secondary);
    box-shadow: 0 0 20px rgba(59, 130, 246, 0.2);
}

/* ========================================
   Pagination
   ======================================== */
.pagination {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    margin-top: var(--spacing-12);
}

.pagination-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 44px;
    height: 44px;
    padding: 0 var(--spacing-3);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-text-muted);
    background: linear-gradient(145deg, var(--color-surface) 0%, var(--color-primary-light) 100%);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    transition: all var(--transition-normal);
}

.pagination-btn:hover {
    border-color: var(--color-secondary);
    color: var(--color-secondary);
    transform: translateY(-2px);
}

.pagination-btn.active {
    background: linear-gradient(135deg, var(--color-secondary) 0%, rgba(139, 92, 246, 0.8) 100%);
    border-color: var(--color-secondary);
    color: white;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.4);
}

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

.pagination-btn svg {
    width: 18px;
    height: 18px;
}

/* ========================================
   Empty State
   ======================================== */
.empty-state {
    text-align: center;
    padding: var(--spacing-16) var(--spacing-4);
    background: linear-gradient(145deg, rgba(30, 41, 59, 0.3) 0%, rgba(15, 23, 42, 0.5) 100%);
    border-radius: var(--radius-2xl);
    border: 1px dashed var(--color-border);
}

.empty-icon {
    width: 100px;
    height: 100px;
    margin: 0 auto var(--spacing-6);
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.15) 0%, rgba(139, 92, 246, 0.15) 100%);
    border: 1px solid rgba(59, 130, 246, 0.3);
    border-radius: var(--radius-full);
    color: var(--color-secondary);
}

.empty-icon svg {
    width: 40px;
    height: 40px;
}

.empty-title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-2);
}

.empty-desc {
    font-size: var(--font-size-base);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-6);
}

/* ========================================
   Footer
   ======================================== */
.footer {
    background: linear-gradient(180deg, var(--color-background) 0%, var(--color-primary-light) 50%, var(--color-primary) 100%);
    color: white;
    padding: var(--spacing-16) 0 var(--spacing-8);
    margin-top: auto;
    border-top: 1px solid var(--color-border);
    position: relative;
}

.footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--color-secondary), transparent);
}

.footer-grid {
    display: grid;
    gap: var(--spacing-8);
    margin-bottom: var(--spacing-12);
}

@media (min-width: 768px) {
    .footer-grid {
        grid-template-columns: 2fr repeat(3, 1fr);
    }
}

.footer-brand .logo {
    margin-bottom: var(--spacing-4);
    color: white;
}

.footer-desc {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.7);
    line-height: 1.7;
}

.footer-links h4 {
    font-size: var(--font-size-sm);
    font-weight: 600;
    margin-bottom: var(--spacing-4);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.footer-links ul {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-3);
}

.footer-links a {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.7);
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: white;
}

.footer-bottom {
    padding-top: var(--spacing-8);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
}

.footer-bottom p {
    font-size: var(--font-size-sm);
    color: rgba(255, 255, 255, 0.5);
}

/* ========================================
   Utilities
   ======================================== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mb-0 { margin-bottom: 0; }
.mb-4 { margin-bottom: var(--spacing-4); }
.mb-8 { margin-bottom: var(--spacing-8); }

.mt-0 { margin-top: 0; }
.mt-4 { margin-top: var(--spacing-4); }
.mt-8 { margin-top: var(--spacing-8); }

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}