/* BERK Learn - Modern Dark Theme */
:root {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --text-primary: #f0f6fc;
    --text-secondary: #8b949e;
    --accent: #58a6ff;
    --accent-hover: #79b8ff;
    --success: #3fb950;
    --warning: #d29922;
    --error: #f85149;
    --border: #30363d;
    --code-bg: #0d1117;
    --gradient-start: #1a1f35;
    --gradient-end: #0d1117;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

code, pre {
    font-family: 'JetBrains Mono', monospace;
}

/* Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 2rem;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 700;
    font-size: 1.25rem;
}

.logo {
    font-size: 1.5rem;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.2s;
}

.nav-links a:hover {
    color: var(--accent);
}

.lang-switch {
    display: flex;
    gap: 0.25rem;
    background: var(--bg-tertiary);
    padding: 0.25rem;
    border-radius: 6px;
}

.lang-btn {
    padding: 0.5rem 1rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    border-radius: 4px;
    font-weight: 500;
    transition: all 0.2s;
}

.lang-btn.active {
    background: var(--accent);
    color: var(--bg-primary);
}

/* Level Switch */
.level-switch {
    display: flex;
    gap: 0.25rem;
    background: var(--bg-tertiary);
    padding: 0.25rem;
    border-radius: 8px;
    margin-right: 1rem;
}

.level-btn {
    padding: 0.4rem 0.75rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 500;
    transition: all 0.2s;
    white-space: nowrap;
}

.level-btn:hover {
    background: rgba(255,255,255,0.1);
}

.level-btn.active {
    color: var(--bg-primary);
}

.level-btn[data-level="ortaokul"].active {
    background: linear-gradient(135deg, #f093fb, #f5576c);
}

.level-btn[data-level="lise"].active {
    background: linear-gradient(135deg, #4facfe, #00f2fe);
}

.level-btn[data-level="universite"].active {
    background: linear-gradient(135deg, #667eea, #764ba2);
}

/* Level Info Box */
.level-info-box {
    margin-top: 2rem;
    width: 100%;
}

.level-info {
    display: none;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    border-radius: 10px;
    font-size: 0.95rem;
    animation: fadeIn 0.3s ease;
}

.level-info.ortaokul-info {
    background: linear-gradient(135deg, rgba(240,147,251,0.2), rgba(245,87,108,0.2));
    border: 1px solid rgba(245,87,108,0.3);
}

.level-info.lise-info {
    background: linear-gradient(135deg, rgba(79,172,254,0.2), rgba(0,242,254,0.2));
    border: 1px solid rgba(0,242,254,0.3);
}

.level-info.universite-info {
    background: linear-gradient(135deg, rgba(102,126,234,0.2), rgba(118,75,162,0.2));
    border: 1px solid rgba(118,75,162,0.3);
}

.level-badge {
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.85rem;
    white-space: nowrap;
}

.ortaokul-info .level-badge {
    background: linear-gradient(135deg, #f093fb, #f5576c);
    color: white;
}

.lise-info .level-badge {
    background: linear-gradient(135deg, #4facfe, #00f2fe);
    color: #0d1117;
}

.universite-info .level-badge {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
}

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

/* Hero */
.hero {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    padding: 6rem 4rem;
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    min-height: 80vh;
    align-items: center;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1rem;
    background: linear-gradient(90deg, var(--accent), #a371f7);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--accent);
    margin-bottom: 1rem;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    max-width: 500px;
}

.cta-button {
    display: inline-block;
    padding: 1rem 2rem;
    background: var(--accent);
    color: var(--bg-primary);
    text-decoration: none;
    border-radius: 8px;
    font-weight: 600;
    font-size: 1.125rem;
    transition: all 0.2s;
}

.cta-button:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(88, 166, 255, 0.3);
}

.hero-code {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 2rem;
    overflow-x: auto;
}

.hero-code pre {
    margin: 0;
}

.hero-code code {
    font-size: 0.95rem;
    line-height: 1.8;
}

/* Syntax highlighting */
.keyword { color: #ff7b72; }
.function { color: #d2a8ff; }
.string { color: #a5d6ff; }
.comment { color: #8b949e; }
.number { color: #79c0ff; }
.type { color: #7ee787; }

/* Features */
.features {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    padding: 4rem;
    background: var(--bg-secondary);
}

.feature-card {
    background: var(--bg-tertiary);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid var(--border);
    transition: all 0.3s;
}

.feature-card:hover {
    border-color: var(--accent);
    transform: translateY(-4px);
}

.feature-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.feature-card p {
    color: var(--text-secondary);
}

.feature-card code {
    background: var(--code-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-size: 0.875rem;
    color: var(--accent);
}

/* Lessons */
.lessons {
    padding: 4rem;
}

.lessons h2 {
    font-size: 2rem;
    margin-bottom: 2rem;
    text-align: center;
}

.lessons-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    max-width: 1200px;
    margin: 0 auto;
}

.lesson-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.5rem;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s;
    position: relative;
    overflow: hidden;
}

.lesson-card:hover {
    border-color: var(--accent);
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3);
}

.lesson-number {
    position: absolute;
    top: 1rem;
    right: 1rem;
    font-size: 2rem;
    font-weight: 700;
    color: var(--bg-tertiary);
}

.lesson-card h3 {
    font-size: 1.125rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.lesson-card p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* About */
.about {
    padding: 4rem;
    background: var(--bg-secondary);
}

.about h2 {
    font-size: 2rem;
    margin-bottom: 2rem;
    text-align: center;
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.about-content p {
    color: var(--text-secondary);
    font-size: 1.125rem;
    margin-bottom: 2rem;
}

.stats {
    display: flex;
    justify-content: center;
    gap: 4rem;
}

.stat {
    text-align: center;
}

.stat-value {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent);
}

.stat-label {
    color: var(--text-secondary);
}

/* Footer */
.footer {
    padding: 2rem;
    text-align: center;
    border-top: 1px solid var(--border);
}

.footer p {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.footer a {
    color: var(--accent);
    text-decoration: none;
}

.footer a:hover {
    text-decoration: underline;
}

/* Lesson Page Styles */
.lesson-header {
    padding: 4rem;
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
}

.lesson-nav {
    display: flex;
    justify-content: space-between;
    margin-bottom: 2rem;
}

.lesson-nav a {
    color: var(--accent);
    text-decoration: none;
}

.lesson-title {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.lesson-meta {
    color: var(--text-secondary);
}

.lesson-content {
    max-width: 900px;
    margin: 0 auto;
    padding: 4rem 2rem;
}

.lesson-section {
    margin-bottom: 3rem;
}

.lesson-section h2 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border);
}

.lesson-section h3 {
    font-size: 1.25rem;
    margin: 1.5rem 0 1rem;
    color: var(--accent);
}

.lesson-section p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.code-block {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    margin: 1.5rem 0;
    overflow: hidden;
}

.code-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border);
}

.code-lang {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
}

.code-block pre {
    padding: 1.5rem;
    overflow-x: auto;
    margin: 0;
}

.code-block code {
    font-size: 0.9rem;
    line-height: 1.7;
}

.example-box {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 2rem;
    margin: 2rem 0;
}

.example-box h4 {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    color: var(--success);
}

.tip-box {
    background: rgba(88, 166, 255, 0.1);
    border-left: 4px solid var(--accent);
    padding: 1rem 1.5rem;
    margin: 1.5rem 0;
    border-radius: 0 8px 8px 0;
}

.tip-box strong {
    color: var(--accent);
}

.exercise-box {
    background: rgba(210, 153, 34, 0.1);
    border-left: 4px solid var(--warning);
    padding: 1.5rem;
    margin: 2rem 0;
    border-radius: 0 8px 8px 0;
}

.exercise-box h4 {
    color: var(--warning);
    margin-bottom: 1rem;
}

.lesson-footer {
    display: flex;
    justify-content: space-between;
    padding: 2rem 4rem;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
}

.lesson-footer a {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--accent);
    text-decoration: none;
    padding: 1rem 1.5rem;
    background: var(--bg-tertiary);
    border-radius: 8px;
    transition: all 0.2s;
}

.lesson-footer a:hover {
    background: var(--accent);
    color: var(--bg-primary);
}

/* Responsive */
@media (max-width: 1024px) {
    .hero {
        grid-template-columns: 1fr;
        padding: 4rem 2rem;
    }
    
    .hero-code {
        display: none;
    }
    
    .features {
        grid-template-columns: 1fr;
        padding: 2rem;
    }
    
    .stats {
        flex-direction: column;
        gap: 2rem;
    }
}

@media (max-width: 768px) {
    .navbar {
        flex-wrap: wrap;
        gap: 1rem;
    }
    
    .nav-links {
        order: 3;
        width: 100%;
        justify-content: center;
    }
    
    .level-switch {
        order: 4;
        width: 100%;
        justify-content: center;
        margin: 0.5rem 0;
    }
    
    .level-btn {
        font-size: 0.75rem;
        padding: 0.3rem 0.5rem;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .lessons-grid {
        grid-template-columns: 1fr;
    }
    
    .lesson-footer {
        flex-direction: column;
        gap: 1rem;
    }
    
    .level-info {
        flex-direction: column;
        text-align: center;
    }
}

/* Language toggle animation */
.tr, .en {
    transition: opacity 0.3s ease;
}

.fade-out {
    opacity: 0;
}

/* Level content visibility */
.ortaokul-content,
.lise-content,
.universite-content {
    animation: fadeIn 0.3s ease;