/* ===================================
   CSS Custom Properties & Reset
   =================================== */
:root {
    /* Colors */
    --bg-primary: #0a0a0f;
    --bg-secondary: #13131a;
    --bg-card: rgba(25, 25, 35, 0.6);
    --bg-card-hover: rgba(35, 35, 50, 0.8);
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-accent: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);
    
    /* Text Colors */
    --text-primary: #ffffff;
    --text-secondary: #b4b4c8;
    --text-muted: #7a7a8c;
    
    /* Accent Colors */
    --accent-purple: #667eea;
    --accent-pink: #f093fb;
    --accent-cyan: #00f2fe;
    --accent-blue: #4facfe;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.3);
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
}

h1 { font-size: clamp(2.5rem, 5vw, 4rem); }
h2 { font-size: clamp(2rem, 4vw, 3rem); }
h3 { font-size: clamp(1.5rem, 3vw, 2rem); }
h4 { font-size: clamp(1.25rem, 2.5vw, 1.5rem); }

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

a:hover {
    color: var(--accent-blue);
}

/* ===================================
   Utility Classes
   =================================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-lg);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 80px;
    height: 4px;
    background: var(--gradient-accent);
    margin: var(--spacing-sm) auto 0;
    border-radius: 2px;
}

/* ===================================
   Navigation
   =================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(10, 10, 15, 0.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    padding: var(--spacing-sm) 0;
    transition: var(--transition-normal);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--spacing-md);
}

.nav-links a {
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: var(--transition-fast);
}

.nav-links a:hover {
    color: var(--text-primary);
    background: rgba(102, 126, 234, 0.1);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
    padding-top: 80px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--gradient-hero);
    opacity: 0.1;
    z-index: 0;
}

.hero-background::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle, rgba(102, 126, 234, 0.3) 0%, transparent 70%);
    animation: float 20s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) rotate(0deg); }
    33% { transform: translate(30px, -30px) rotate(120deg); }
    66% { transform: translate(-20px, 20px) rotate(240deg); }
}

.hero-content {
    position: relative;
    z-index: 1;
}

.hero-text {
    max-width: 800px;
}

.hero-greeting {
    font-size: 1.2rem;
    color: var(--accent-cyan);
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
}

.hero-name {
    margin-bottom: var(--spacing-xs);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-title {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    font-weight: 600;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
}

.btn {
    padding: 1rem 2rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition-normal);
    border: none;
    display: inline-block;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--text-primary);
    box-shadow: var(--shadow-md);
}

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

.btn-secondary {
    background: transparent;
    color: var(--text-primary);
    border: 2px solid var(--accent-purple);
}

.btn-secondary:hover {
    background: rgba(102, 126, 234, 0.1);
    transform: translateY(-2px);
}

.hero-social {
    display: flex;
    gap: var(--spacing-sm);
}

.hero-social a {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    transition: var(--transition-normal);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.hero-social a:hover {
    background: var(--gradient-primary);
    color: var(--text-primary);
    transform: translateY(-4px);
    box-shadow: var(--shadow-glow);
}

/* ===================================
   About Section
   =================================== */
.about {
    padding: var(--spacing-xl) 0;
    background: var(--bg-secondary);
}

.about-content {
    max-width: 900px;
    margin: 0 auto;
}

.about-text p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

.about-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.stat-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-md);
    border-radius: var(--radius-lg);
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.stat-card:hover {
    transform: translateY(-8px);
    background: var(--bg-card-hover);
    box-shadow: var(--shadow-glow);
}

.stat-card h3 {
    font-size: 3rem;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.stat-card p {
    color: var(--text-secondary);
    font-weight: 500;
}

/* ===================================
   Experience Section
   =================================== */
.experience {
    padding: var(--spacing-xl) 0;
}

.timeline {
    max-width: 900px;
    margin: 0 auto;
    position: relative;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--gradient-primary);
}

.timeline-item {
    position: relative;
    padding-left: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.timeline-dot {
    position: absolute;
    left: -8px;
    top: 8px;
    width: 18px;
    height: 18px;
    background: var(--gradient-primary);
    border-radius: 50%;
    box-shadow: 0 0 0 4px var(--bg-primary);
}

.timeline-content {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-md);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.timeline-content:hover {
    background: var(--bg-card-hover);
    transform: translateX(8px);
    box-shadow: var(--shadow-lg);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-xs);
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.timeline-header h3 {
    color: var(--text-primary);
    font-size: 1.3rem;
}

.timeline-date {
    color: var(--accent-cyan);
    font-weight: 600;
    font-size: 0.9rem;
}

.timeline-content h4 {
    color: var(--text-secondary);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.timeline-content ul {
    list-style: none;
    padding-left: 0;
}

.timeline-content li {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
    padding-left: 1.5rem;
    position: relative;
}

.timeline-content li::before {
    content: '▹';
    position: absolute;
    left: 0;
    color: var(--accent-cyan);
    font-weight: bold;
}

/* ===================================
   Projects Section
   =================================== */
.projects {
    padding: var(--spacing-xl) 0;
    background: var(--bg-secondary);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: var(--spacing-md);
}

.project-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-md);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
    display: flex;
    flex-direction: column;
}

.project-card:hover {
    transform: translateY(-8px);
    background: var(--bg-card-hover);
    box-shadow: var(--shadow-glow);
    border-color: var(--accent-purple);
}

.project-header {
    margin-bottom: var(--spacing-sm);
}

.project-header h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    font-size: 1.3rem;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-sm);
}

.tag {
    background: rgba(102, 126, 234, 0.2);
    color: var(--accent-cyan);
    padding: 0.3rem 0.8rem;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 500;
}

.project-card > p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    line-height: 1.6;
}

.project-card ul {
    list-style: none;
    padding-left: 0;
    margin-bottom: var(--spacing-sm);
    flex-grow: 1;
}

.project-card li {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
    padding-left: 1.5rem;
    position: relative;
    font-size: 0.95rem;
}

.project-card li::before {
    content: '▹';
    position: absolute;
    left: 0;
    color: var(--accent-cyan);
    font-weight: bold;
}

.project-link {
    color: var(--accent-cyan);
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    margin-top: auto;
    transition: var(--transition-fast);
}

.project-link:hover {
    color: var(--accent-blue);
    transform: translateX(4px);
}

/* ===================================
   Skills Section
   =================================== */
.skills {
    padding: var(--spacing-xl) 0;
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
}

.skill-category {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-md);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.skill-category:hover {
    background: var(--bg-card-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.skill-category h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    font-size: 1.2rem;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.skill-tag {
    background: rgba(102, 126, 234, 0.15);
    color: var(--text-secondary);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition-fast);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.skill-tag:hover {
    background: var(--gradient-primary);
    color: var(--text-primary);
    transform: translateY(-2px);
}

/* ===================================
   Education Section
   =================================== */
.education {
    padding: var(--spacing-xl) 0;
    background: var(--bg-secondary);
}

.education-content {
    max-width: 900px;
    margin: 0 auto;
}

.education-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.education-card:hover {
    background: var(--bg-card-hover);
    box-shadow: var(--shadow-glow);
}

.education-card h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
    font-size: 1.5rem;
}

.education-card h4 {
    color: var(--accent-purple);
    margin-bottom: var(--spacing-xs);
    font-weight: 600;
}

.education-date {
    color: var(--accent-cyan);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.education-specialization {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    font-style: italic;
}

.research-papers {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.research-papers h5 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.research-papers ul {
    list-style: none;
    padding-left: 0;
}

.research-papers li {
    margin-bottom: var(--spacing-sm);
    padding-left: 1.5rem;
    position: relative;
}

.research-papers li::before {
    content: '📄';
    position: absolute;
    left: 0;
}

.research-papers a {
    color: var(--accent-cyan);
    transition: var(--transition-fast);
}

.research-papers a:hover {
    color: var(--accent-blue);
    text-decoration: underline;
}

/* ===================================
   Contact Section
   =================================== */
.contact {
    padding: var(--spacing-xl) 0;
}

.contact-content {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.contact-description {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.contact-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.contact-item {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.contact-item:hover {
    background: var(--bg-card-hover);
    transform: translateX(8px);
}

.contact-item svg {
    color: var(--accent-cyan);
    flex-shrink: 0;
}

.contact-item a,
.contact-item span {
    color: var(--text-secondary);
    font-weight: 500;
}

.contact-social {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.social-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-secondary);
    font-weight: 600;
    transition: var(--transition-normal);
}

.social-link:hover {
    background: var(--gradient-primary);
    color: var(--text-primary);
    transform: translateY(-4px);
    box-shadow: var(--shadow-glow);
}

/* ===================================
   Footer
   =================================== */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-md) 0;
    text-align: center;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero {
        min-height: auto;
        padding: var(--spacing-xl) 0;
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        text-align: center;
    }
    
    .timeline::before {
        left: 8px;
    }
    
    .timeline-item {
        padding-left: var(--spacing-md);
    }
    
    .timeline-dot {
        left: 0;
    }
    
    .projects-grid {
        grid-template-columns: 1fr;
    }
    
    .skills-grid {
        grid-template-columns: 1fr;
    }
    
    .about-stats {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    :root {
        --spacing-lg: 3rem;
        --spacing-xl: 4rem;
    }
    
    .container {
        padding: 0 var(--spacing-sm);
    }
    
    .hero-name {
        font-size: 2rem;
    }
    
    .hero-title {
        font-size: 1.5rem;
    }
}