/* Theme Variables */
:root {
    --bg: #ffffff;
    --text: #1f2937;
    --text-muted: #4b5563;
    --text-strong: #111827;
    --section-bg: #f9fafb;
    --surface: #ffffff;
    --header-bg: rgba(255, 255, 255, 0.95);
    --border: #e5e7eb;
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --accent-contrast: #ffffff;
    --tag-bg: #e0f2fe;
    --tag-text: #0277bd;
    --tech-tag-bg: #f3f4f6;
    --tech-tag-text: #374151;
    --footer-bg: #1f2937;
    --footer-text: #9ca3af;
    --hero-bg: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
}

html[data-theme="dark"] {
    --bg: #0b1220;
    --text: #e5e7eb;
    --text-muted: #94a3b8;
    --text-strong: #f8fafc;
    --section-bg: #0d162a;
    --surface: #111827;
    --header-bg: rgba(17, 24, 39, 0.9);
    --border: #1f2937;
    --accent: #60a5fa;
    --accent-hover: #3b82f6;
    --accent-contrast: #0b1220;
    --tag-bg: #1e293b;
    --tag-text: #93c5fd;
    --tech-tag-bg: #1f2937;
    --tech-tag-text: #cbd5e1;
    --footer-bg: #0b1220;
    --footer-text: #94a3b8;
    --hero-bg: linear-gradient(135deg, #0b1220 0%, #111827 100%);
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background-color: var(--bg);
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--header-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: all 0.3s ease;
}

.header.scrolled {
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.2);
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.nav-brand h2 {
    font-weight: 600;
    color: var(--text-strong);
    font-size: 1.5rem;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.theme-btn {
    padding: 0.5rem 0.9rem;
    border: 2px solid var(--accent);
    background: transparent;
    color: var(--accent);
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s ease;
    font-size: 0.9rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.theme-btn:hover {
    background: var(--accent);
    color: var(--accent-contrast);
    transform: translateY(-1px);
}

.language-switcher {
    display: flex;
    gap: 0.5rem;
}

.lang-btn {
    padding: 0.5rem 1rem;
    border: 2px solid var(--accent);
    background: transparent;
    color: var(--accent);
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s ease;
    font-size: 0.9rem;
}

.lang-btn:hover {
    background: var(--accent);
    color: var(--accent-contrast);
    transform: translateY(-1px);
}

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

/* Hero Section */
.hero {
    padding: 120px 0 80px;
    background: var(--hero-bg);
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--text-strong);
    margin-bottom: 1rem;
    animation: fadeInUp 0.8s ease;
}

.hero-tagline {
    font-size: 1.25rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
    animation: fadeInUp 0.8s ease 0.2s both;
}

.hero-subline {
    font-size: 1rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
    animation: fadeInUp 0.8s ease 0.3s both;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease 0.4s both;
}

.btn {
    padding: 0.75rem 2rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    display: inline-block;
    border: 2px solid transparent;
}

.btn-primary {
    background: var(--accent);
    color: var(--accent-contrast);
    border-color: var(--accent);
}

.btn-primary:hover {
    background: var(--accent-hover);
    border-color: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(59, 130, 246, 0.3);
}

.btn-secondary {
    background: transparent;
    color: var(--accent);
    border-color: var(--accent);
}

.btn-secondary:hover {
    background: var(--accent);
    color: var(--accent-contrast);
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(59, 130, 246, 0.2);
}

/* Sections */
section {
    padding: 80px 0;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 600;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--text-strong);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background: var(--accent);
    border-radius: 2px;
}

/* About Section */
.about {
    background: var(--section-bg);
}

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

.about-text {
    font-size: 1.125rem;
    color: var(--text-muted);
    line-height: 1.8;
}

/* Skills Section */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.skill-category {
    background: var(--surface);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.skill-category:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
}

.skill-category h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-strong);
    margin-bottom: 1rem;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.skill-tag {
    background: var(--tag-bg);
    color: var(--tag-text);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.skill-tag:hover {
    background: var(--accent);
    color: var(--accent-contrast);
    transform: scale(1.05);
}

/* Projects Section */
.projects {
    background: var(--section-bg);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.project-card {
    background: var(--surface);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.project-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
}

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

.project-header h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-strong);
    flex: 1;
}

.project-links {
    display: flex;
    gap: 0.5rem;
}

.project-link {
    color: var(--text-muted);
    font-size: 1.25rem;
    transition: color 0.3s ease, transform 0.3s ease;
}

.project-link:hover {
    color: var(--accent);
    transform: scale(1.1);
}

.project-description {
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.project-note {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin: -0.5rem 0 1.25rem;
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.tech-tag {
    background: var(--tech-tag-bg);
    color: var(--tech-tag-text);
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 500;
}

.project-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.action-btn {
    display: inline-block;
    padding: 0.5rem 0.9rem;
    border-radius: 8px;
    background: var(--accent);
    color: var(--accent-contrast);
    border: 2px solid var(--accent);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.2s ease;
}

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

.action-btn.outline {
    background: transparent;
    color: var(--accent);
}

.action-btn.outline:hover {
    background: var(--accent);
    color: var(--accent-contrast);
}

/* Education Section */
.education-item {
    max-width: 800px;
    margin: 0 auto;
    background: var(--surface);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
}

.education-content h3 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-strong);
    margin-bottom: 0.5rem;
}

.education-institution {
    font-size: 1.125rem;
    color: var(--accent);
    font-weight: 500;
    margin-bottom: 0.25rem;
}

.education-year {
    color: var(--text-muted);
    font-weight: 500;
    margin-bottom: 1rem;
}

.education-description {
    color: var(--text-muted);
    line-height: 1.6;
}

/* Contact Section */
.contact {
    background: var(--section-bg);
}

.contact-content {
    max-width: 600px;
    margin: 0 auto;
    text-align: center;
}

.contact-text {
    font-size: 1.125rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.contact-links {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    align-items: center;
}

.contact-link {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem 1.5rem;
    background: var(--surface);
    color: var(--text);
    text-decoration: none;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.15);
    transition: all 0.3s ease;
    min-width: 250px;
    justify-content: center;
}

.contact-link:hover {
    background: var(--accent);
    color: var(--accent-contrast);
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(59, 130, 246, 0.3);
}

.contact-link i {
    font-size: 1.25rem;
}

/* Footer */
.footer {
    background: var(--footer-bg);
    color: var(--footer-text);
    text-align: center;
    padding: 2rem 0;
}

/* Animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav {
        padding: 1rem;
    }
    
    .nav-brand h2 {
        font-size: 1.25rem;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-tagline {
        font-size: 1.125rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .btn {
        width: 100%;
        max-width: 250px;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .skills-grid {
        grid-template-columns: 1fr;
    }
    
    .projects-grid {
        grid-template-columns: 1fr;
    }
    
    .project-header {
        flex-direction: column;
        gap: 1rem;
    }
    
    .contact-links {
        gap: 0.75rem;
    }
    
    .contact-link {
        min-width: auto;
        width: 100%;
        max-width: 300px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    .hero {
        padding: 100px 0 60px;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    section {
        padding: 60px 0;
    }
    
    .skill-category,
    .project-card,
    .education-item {
        padding: 1.5rem;
    }
    
    .lang-btn {
        padding: 0.4rem 0.8rem;
        font-size: 0.8rem;
    }
}

/* Smooth transitions for language switching */
[data-en], [data-de] {
    transition: opacity 0.3s ease;
}

/* Loading state */
.loading {
    opacity: 0.7;
    pointer-events: none;
}