/* ===================================
   CSS Variables (Design System)
   =================================== */
:root {
    /* Colors - Scientific Dark Theme */
    --color-primary: #00D9FF;          /* Bright cyan - ML/AI accent */
    --color-secondary: #6C63FF;        /* Purple - research accent */
    --color-accent: #FF6B9D;           /* Pink - highlights */
    
    --color-bg-dark: #0A0E27;          /* Deep navy background */
    --color-bg-light: #151A35;         /* Card background */
    --color-bg-lighter: #1E2547;       /* Hover states */
    
    --color-text-primary: #E8EDF4;     /* Main text */
    --color-text-secondary: #A0AEC0;   /* Secondary text */
    --color-text-muted: #718096;       /* Muted text */
    
    /* Typography */
    --font-display: 'Playfair Display', serif;
    --font-body: 'Source Sans Pro', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    
    /* Layout */
    --max-width: 1200px;
    --border-radius: 12px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* 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 20px rgba(0, 217, 255, 0.3);
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-body);
    background-color: var(--color-bg-dark);
    color: var(--color-text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-display);
    font-weight: 700;
    line-height: 1.2;
    color: var(--color-text-primary);
}

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: 1.25rem; }

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

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

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

/* ===================================
   Layout Utilities
   =================================== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section {
    padding: var(--spacing-xl) 0;
}

.section-dark {
    background-color: var(--color-bg-light);
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-md);
    font-size: 2.5rem;
    position: relative;
    display: inline-block;
    left: 50%;
    transform: translateX(-50%);
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
    margin: 1rem auto 0;
    border-radius: 2px;
}

.section-intro {
    text-align: center;
    max-width: 700px;
    margin: 0 auto var(--spacing-lg);
    font-size: 1.1rem;
    color: var(--color-text-secondary);
}

/* ===================================
   Navigation
   =================================== */
#navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(10, 14, 39, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    transition: var(--transition-normal);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

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

.nav-logo {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 900;
    color: var(--color-primary);
    text-transform: uppercase;
    letter-spacing: 2px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-link {
    color: var(--color-text-primary);
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-primary);
    transition: var(--transition-normal);
}

.nav-link:hover::after {
    width: 100%;
}

/* Hamburger Menu (Mobile) */
.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger .bar {
    width: 25px;
    height: 3px;
    background-color: var(--color-text-primary);
    margin: 3px 0;
    transition: var(--transition-normal);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    padding-top: 80px;
    background: linear-gradient(135deg, var(--color-bg-dark) 0%, #0D1433 100%);
    overflow: hidden;
}

/* Animated background gradient */
.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(0, 217, 255, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(108, 99, 255, 0.1) 0%, transparent 50%);
    animation: gradientShift 15s ease infinite;
}

@keyframes gradientShift {
    0%, 100% { opacity: 0.5; transform: scale(1); }
    50% { opacity: 0.8; transform: scale(1.1); }
}

.hero-content {
    position: relative;
    z-index: 2;
    text-align: center;
    max-width: 900px;
    padding: 0 var(--spacing-md);
}

.hero-name {
    display: block;
    font-size: clamp(3rem, 6vw, 5rem);
    font-weight: 900;
    background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
    animation: fadeInUp 0.8s ease;
    font-size: clamp(1.2rem, 3vw, 2rem);
}

.hero-subtitle {
    font-size: clamp(1.2rem, 2.5vw, 1.8rem);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    font-weight: 300;
    letter-spacing: 1px;
    animation: fadeInUp 0.8s ease 0.2s both;
}

.hero-description {
    font-size: 1.1rem;
    max-width: 700px;
    margin: 0 auto var(--spacing-lg);
    line-height: 1.8;
    animation: fadeInUp 0.8s ease 0.4s both;
}

.hero-cta {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: var(--spacing-md);
    animation: fadeInUp 0.8s ease 0.6s both;
}

.hero-social {
    display: flex;
    gap: 1.5rem;
    justify-content: center;
    animation: fadeInUp 0.8s ease 0.8s both;
}

.hero-social a {
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--color-primary);
    border-radius: 50%;
    color: var(--color-primary);
    font-size: 1.3rem;
    transition: var(--transition-normal);
}

.hero-social a:hover {
    background: var(--color-primary);
    color: var(--color-bg-dark);
    transform: translateY(-5px);
    box-shadow: var(--shadow-glow);
}

.scroll-indicator {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    color: var(--color-text-muted);
    font-size: 0.9rem;
    animation: bounce 2s infinite;
}

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

@keyframes bounce {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(-10px); }
}

/* ===================================
   Buttons
   =================================== */
.btn {
    display: inline-block;
    padding: 0.9rem 2rem;
    border-radius: var(--border-radius);
    font-weight: 600;
    text-align: center;
    cursor: pointer;
    transition: var(--transition-normal);
    border: 2px solid transparent;
    font-size: 1rem;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
    color: var(--color-bg-dark);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-glow);
}

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

.btn-secondary:hover {
    background: var(--color-primary);
    color: var(--color-bg-dark);
}

/* ===================================
   About Section
   =================================== */
.about-content {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: var(--spacing-lg);
    align-items: start;
}

.about-image {
    position: relative;
}

.about-image img {
    width: 100%;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    border: 3px solid var(--color-primary);
}

.about-text {
    font-size: 1.05rem;
}

.about-intro {
    font-size: 1.15rem;
    margin-bottom: var(--spacing-md);
    color: var(--color-text-primary);
}

.subsection-title {
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
    color: var(--color-primary);
    font-size: 1.5rem;
}

.education-item {
    margin-bottom: var(--spacing-md);
    padding: var(--spacing-sm);
    background: var(--color-bg-light);
    border-radius: var(--border-radius);
    border-left: 4px solid var(--color-primary);
}

.education-item h4 {
    color: var(--color-text-primary);
    margin-bottom: 0.3rem;
}

.education-meta {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.interests-list {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 0.8rem;
}

.interests-list li {
    padding: 0.6rem 1rem;
    background: var(--color-bg-light);
    border-radius: var(--border-radius);
    color: var(--color-text-secondary);
    border-left: 3px solid var(--color-secondary);
}

/* ===================================
   Research Section
   =================================== */
.research-grid {
    display: grid;
    gap: var(--spacing-md);
}

.research-item {
    background: var(--color-bg-dark);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-normal);
}

.research-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--color-primary);
}

.research-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: var(--spacing-sm);
}

.research-header h3 {
    color: var(--color-text-primary);
    font-size: 1.4rem;
    flex: 1;
}

.research-year {
    background: var(--color-secondary);
    color: white;
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
}

.research-authors {
    color: var(--color-text-secondary);
    font-size: 0.95rem;
    margin-bottom: 0.3rem;
}

.research-venue {
    color: var(--color-primary);
    font-style: italic;
    margin-bottom: var(--spacing-sm);
}

.research-description {
    margin-bottom: var(--spacing-sm);
}

.research-links {
    display: flex;
    gap: 1rem;
    margin-bottom: var(--spacing-sm);
}

.research-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.4rem 1rem;
    background: var(--color-bg-lighter);
    border-radius: 20px;
    font-size: 0.9rem;
    transition: var(--transition-fast);
}

.research-link:hover {
    background: var(--color-primary);
    color: var(--color-bg-dark);
}

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

/* ===================================
   Projects Section
   =================================== */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-md);
}

.project-card {
    background: var(--color-bg-light);
    border-radius: var(--border-radius);
    overflow: hidden;
    transition: var(--transition-normal);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.project-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
}

.project-image {
    position: relative;
    overflow: hidden;
    height: 220px;
    background: var(--color-bg-dark);
}

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

.project-card:hover .project-image img {
    transform: scale(1.1);
}

.project-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    opacity: 0;
    transition: var(--transition-normal);
}

.project-card:hover .project-overlay {
    opacity: 1;
}

.project-link {
    width: 50px;
    height: 50px;
    background: var(--color-primary);
    color: var(--color-bg-dark);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-size: 1.2rem;
    transition: var(--transition-fast);
}

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

.project-content {
    padding: var(--spacing-md);
}

.project-title {
    margin-bottom: var(--spacing-sm);
    color: var(--color-text-primary);
}

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

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

.tech-tag {
    padding: 0.4rem 0.9rem;
    background: var(--color-bg-dark);
    color: var(--color-primary);
    border-radius: 20px;
    font-size: 0.85rem;
    border: 1px solid var(--color-primary);
}

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

.skill-category {
    background: var(--color-bg-dark);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.skill-category-title {
    display: flex;
    align-items: center;
    gap: 0.8rem;
    margin-bottom: var(--spacing-md);
    color: var(--color-primary);
    font-size: 1.3rem;
}

.skill-category-title i {
    font-size: 1.5rem;
}

.skill-items {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.skill-item {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

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

.skill-bar {
    height: 8px;
    background: var(--color-bg-lighter);
    border-radius: 10px;
    overflow: hidden;
}

.skill-level {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
    border-radius: 10px;
    transition: width 1s ease;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
}

.tag {
    padding: 0.5rem 1rem;
    background: var(--color-bg-lighter);
    color: var(--color-text-secondary);
    border-radius: 20px;
    font-size: 0.9rem;
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-fast);
}

.tag:hover {
    background: var(--color-primary);
    color: var(--color-bg-dark);
    border-color: var(--color-primary);
}

/* ===================================
   Contact Section
   =================================== */
.contact-content {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: var(--spacing-lg);
}

.contact-item {
    display: flex;
    gap: 1.5rem;
    align-items: start;
    margin-bottom: var(--spacing-md);
}

.contact-item i {
    font-size: 2rem;
    color: var(--color-primary);
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg-light);
    border-radius: 50%;
}

.contact-item h3 {
    font-size: 1.1rem;
    margin-bottom: 0.3rem;
}

.contact-item a {
    color: var(--color-text-secondary);
}

.contact-form-container {
    background: var(--color-bg-light);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 1rem;
    background: var(--color-bg-dark);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--border-radius);
    color: var(--color-text-primary);
    font-family: var(--font-body);
    font-size: 1rem;
    transition: var(--transition-fast);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 217, 255, 0.1);
}

.form-group textarea {
    resize: vertical;
}

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

.footer p {
    margin-bottom: var(--spacing-sm);
    color: var(--color-text-muted);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
}

.footer-links a {
    color: var(--color-text-secondary);
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 968px) {
    .about-content {
        grid-template-columns: 1fr;
    }
    
    .contact-content {
        grid-template-columns: 1fr;
    }
    
    .projects-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--color-bg-dark);
        width: 100%;
        text-align: center;
        transition: var(--transition-normal);
        box-shadow: var(--shadow-lg);
        padding: 2rem 0;
    }
    
    .nav-menu.active {
        left: 0;
    }
    
    .hamburger {
        display: flex;
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .skills-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    :root {
        font-size: 14px;
    }
    
    .section {
        padding: var(--spacing-md) 0;
    }
    
    .hero-social {
        gap: 1rem;
    }
    
    .hero-social a {
        width: 40px;
        height: 40px;
        font-size: 1.1rem;
    }
}
/* End of styles.css */