:root {
    --primary-color: #2563eb;
    --secondary-color: #64748b;
    --dark-color: #0f172a;
    --light-color: #f8fafc;
    --accent-color: #3b82f6;
    --text-color: #334155;
    --bg-color: #f1f5f9;
    --container-width: 1200px;
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

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

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

section.section {
    padding: 5rem 4rem;
    margin-bottom: 5rem;
    border: 1px solid #e2e8f0;
    border-radius: 32px;
    background-color: #ffffff;
    box-shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.03);
}

/* Alternating background for sections */
section.section:nth-of-type(even) {
    background-color: #f8fafc;
}

.section-title {
    font-size: 2.8rem;
    margin-bottom: 4rem;
    position: relative;
    color: var(--dark-color);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 0;
    width: 50px;
    height: 4px;
    background-color: var(--primary-color);
}

/* Header & Nav */
header {
    background-color: rgba(255, 255, 255, 0.90);
    backdrop-filter: blur(12px);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    width: 90%;
    max-width: 1100px;
    border-radius: 100px;
    border: 1px solid #e2e8f0;
    z-index: 1000;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--dark-color);
    font-weight: 500;
    transition: var(--transition);
}

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

.burger {
    display: none;
    cursor: pointer;
}

.burger div {
    width: 25px;
    height: 3px;
    background-color: var(--dark-color);
    margin: 5px;
    transition: var(--transition);
}

/* Hero Section */
#hero {
    min-height: calc(100vh - 140px);
    margin-top: 100px;
    margin-bottom: 5rem;
    display: flex;
    align-items: center;
    background: linear-gradient(135deg, #ffffff 0%, #f1f5f9 100%);
    padding: 4rem 4rem;
    border: 1px solid #e2e8f0;
    border-radius: 32px;
    box-shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.03);
}

.hero-content {
    text-align: center;
    margin: 0 auto;
}

.hero-image {
    width: 200px;
    height: 200px;
    margin: 0 auto 2rem;
    border-radius: 50%;
    overflow: hidden;
    border: 5px solid white;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

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

.hero-content h1 {
    font-size: 4rem;
    margin-bottom: 1rem;
    color: var(--dark-color);
}

.hero-content h2 {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.hero-content p {
    font-size: 1.2rem;
    max-width: 600px;
    margin: 0 auto 2rem;
}

/* Hero Badges */
.hero-badges {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.8rem;
    margin-bottom: 2.5rem;
}

.badge {
    background-color: rgba(37, 99, 235, 0.08);
    color: var(--primary-color);
    border: 1px solid rgba(37, 99, 235, 0.2);
    padding: 0.45rem 1.1rem;
    border-radius: 100px;
    font-size: 0.88rem;
    font-weight: 500;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

.btn {
    display: inline-block;
    padding: 0.8rem 2rem;
    border-radius: 5px;
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    cursor: pointer;
}

.btn.primary {
    background-color: var(--primary-color);
    color: white;
}

.btn.primary:hover {
    background-color: var(--accent-color);
    transform: translateY(-3px);
}

.btn.secondary {
    background-color: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
    margin-left: 1rem;
}

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

/* Timeline */
.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.timeline::after {
    content: '';
    position: absolute;
    width: 2px;
    background-color: var(--primary-color);
    top: 0;
    bottom: 0;
    left: 20px;
}

.timeline-item {
    padding: 32px 40px;
    position: relative;
    background-color: inherit;
    width: 100%;
}

.timeline-dot {
    position: absolute;
    width: 16px;
    height: 16px;
    left: 13px;
    background-color: white;
    border: 4px solid var(--primary-color);
    top: 25px;
    border-radius: 50%;
    z-index: 1;
}

.timeline-date {
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.8rem;
}

.timeline-content {
    padding: 30px;
    background-color: var(--light-color);
    border-radius: 12px;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.timeline-content h3 {
    margin-bottom: 0.5rem;
    font-size: 1.5rem;
}

.timeline-content h4 {
    color: var(--secondary-color);
    margin-bottom: 2rem;
    font-weight: 500;
}

.timeline-content ul {
    list-style-position: inside;
}

.timeline-content li {
    margin-bottom: 0.5rem;
}

/* About Grid */
.about-grid {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 4rem;
    align-items: start;
}

.about-text p {
    margin-bottom: 1.2rem;
    font-size: 1.05rem;
    line-height: 1.8;
    color: var(--text-color);
}

.about-stats {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.2rem;
}

.stat-card {
    background: var(--light-color);
    border: 1px solid #e2e8f0;
    border-radius: 16px;
    padding: 1.5rem 1rem;
    text-align: center;
    box-shadow: 0 4px 12px rgba(0,0,0,0.04);
    transition: var(--transition);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(37,99,235,0.1);
    border-color: var(--primary-color);
}

.stat-number {
    display: block;
    font-size: 2.4rem;
    font-weight: 700;
    color: var(--primary-color);
    line-height: 1.1;
}

.stat-label {
    display: block;
    font-size: 0.8rem;
    color: var(--secondary-color);
    font-weight: 500;
    margin-top: 0.4rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Volunteer & Cards */
.experience-card {
    background: var(--light-color);
    padding: 3rem;
    border-radius: 12px;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

.experience-card h3 {
    margin-bottom: 0.8rem;
}

.experience-card h4 {
    color: var(--secondary-color);
    margin-bottom: 1.5rem;
}

.experience-card .date {
    margin-bottom: 2rem;
    display: block;
    color: var(--primary-color);
    font-weight: 600;
}

.experience-card ul {
    list-style-position: inside;
}

.experience-card li {
    margin-bottom: 0.8rem;
}

/* Teaching Section */
.teaching-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.teaching-card {
    background: var(--light-color);
    border: 1px solid #e2e8f0;
    border-radius: 16px;
    padding: 1.8rem 2rem;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    transition: var(--transition);
    box-shadow: 0 4px 10px rgba(0,0,0,0.04);
}

.teaching-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(37,99,235,0.1);
    border-color: var(--primary-color);
}

.teaching-icon {
    width: 52px;
    height: 52px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.teaching-icon i {
    color: white;
    font-size: 1.3rem;
}

.teaching-info h3 {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 0.2rem;
}

.teaching-info h4 {
    font-size: 0.95rem;
    color: var(--secondary-color);
    font-weight: 500;
    margin-bottom: 0.4rem;
}

.teaching-info .date {
    font-size: 0.82rem;
    color: var(--primary-color);
    font-weight: 600;
}

/* Technical Talks */
.talks-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(360px, 1fr));
    gap: 2rem;
}

.talk-card {
    background: var(--light-color);
    border: 1px solid #e2e8f0;
    border-radius: 16px;
    padding: 2rem 2.5rem;
    display: flex;
    align-items: flex-start;
    gap: 1.5rem;
    transition: var(--transition);
    box-shadow: 0 4px 10px rgba(0,0,0,0.04);
}

.talk-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(239,68,68,0.1);
    border-color: #ef4444;
}

.talk-icon {
    width: 52px;
    height: 52px;
    background: linear-gradient(135deg, #ef4444, #dc2626);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.talk-icon i {
    color: white;
    font-size: 1.4rem;
}

.talk-info h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 0.4rem;
}

.talk-org {
    font-size: 0.9rem;
    color: var(--secondary-color);
    margin-bottom: 1rem;
}

.talk-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--primary-color);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 600;
    transition: var(--transition);
}

.talk-link:hover {
    color: #ef4444;
    gap: 0.6rem;
}

/* Skills */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2.5rem;
}

.skill-category {
    background: var(--light-color);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

.skill-category h3 {
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.8rem;
}

.tag {
    background-color: white;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    border: 1px solid #e2e8f0;
    transition: var(--transition);
}

.tag:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
}

/* Grid Two Cols */
.grid-two-cols {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
}

.edu-item {
    margin-bottom: 3rem;
}

.edu-item h3 {
    margin-bottom: 0.3rem;
}

.edu-item p {
    color: var(--secondary-color);
}

.cert-list {
    list-style: none;
}

.cert-list li {
    padding: 1rem 0;
    border-bottom: 1px solid #e2e8f0;
    display: flex;
    align-items: flex-start;
    gap: 0.8rem;
    font-size: 0.95rem;
    line-height: 1.5;
}

.cert-list li:last-child {
    border-bottom: none;
}

.cert-icon {
    color: var(--primary-color);
    margin-top: 0.15rem;
    flex-shrink: 0;
    font-size: 0.9rem;
}

/* Awards */
.awards-list {
    list-style: none;
}

.awards-list li {
    font-size: 1.2rem;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
}

.awards-list i {
    color: #fbbf24;
    margin-right: 1rem;
}

/* Footer & Contact */
footer {
    background-color: var(--dark-color);
    color: white;
    padding: 3rem 2rem 2.5rem;
    max-width: var(--container-width);
    margin: 0 auto 2rem;
    border-radius: 32px;
    border: 1px solid var(--dark-color);
    box-shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.1);
}

footer .section-title {
    color: white;
}

footer .section-title::after {
    background-color: var(--primary-color);
}

.contact-links {
    display: flex;
    flex-wrap: wrap;
    gap: 2.5rem;
    margin-bottom: 5rem;
}

.contact-links a,
.contact-links span {
    color: #cbd5e1;
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 0.8rem;
    font-size: 1.1rem;
    transition: var(--transition);
}

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

.languages {
    margin-bottom: 4rem;
    color: #cbd5e1;
}

.copyright {
    text-align: center;
    padding-top: 3rem;
    border-top: 1px solid #334155;
    color: #64748b;
    font-size: 0.9rem;
}

/* Tablet Responsive */
@media screen and (max-width: 1024px) {
    section.section {
        padding: 4rem 2.5rem;
        margin-bottom: 4rem;
    }

    #hero {
        padding: 3rem 2.5rem;
        margin-bottom: 4rem;
    }

    .section-title {
        font-size: 2.4rem;
        margin-bottom: 3.5rem;
    }

    .grid-two-cols {
        gap: 2.5rem;
    }

    .about-grid {
        grid-template-columns: 1fr;
        gap: 2.5rem;
    }
    
    .experience-card {
        padding: 2.5rem;
    }

    .talks-grid {
        grid-template-columns: 1fr;
    }
}

/* Mobile Responsive */
@media screen and (max-width: 768px) {
    .nav-links {
        position: absolute;
        right: 0px;
        height: 92vh;
        top: 8vh;
        background-color: white;
        display: flex;
        flex-direction: column;
        align-items: center;
        width: 65%;
        transform: translateX(100%);
        transition: transform 0.5s ease-in;
        box-shadow: -2px 0 5px rgba(0, 0, 0, 0.1);
    }

    .nav-links li {
        margin: 2rem 0;
    }

    .burger {
        display: block;
    }

    .hero-content h1 {
        font-size: 2.5rem;
    }

    .hero-content h2 {
        font-size: 1.5rem;
    }

    .hero-content p {
        font-size: 1.1rem;
    }

    .grid-two-cols {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .about-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

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

    .teaching-grid {
        grid-template-columns: 1fr;
    }

    .talks-grid {
        grid-template-columns: 1fr;
    }

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

    .toggle .line1 {
        transform: rotate(-45deg) translate(-5px, 6px);
    }

    .toggle .line2 {
        opacity: 0;
    }

    .toggle .line3 {
        transform: rotate(45deg) translate(-5px, -6px);
    }

    @keyframes navLinkFade {
        from {
            opacity: 0;
            transform: translateX(50px);
        }

        to {
            opacity: 1;
            transform: translateX(0);
        }
    }

    section.section {
        padding: 3rem 1.8rem;
        margin-bottom: 3rem;
        border-radius: 24px;
    }

    #hero {
        padding: 3rem 1.8rem;
        border-radius: 24px;
        margin-top: 90px;
        margin-bottom: 3rem;
        min-height: auto;
    }

    .section-title {
        font-size: 2rem;
        margin-bottom: 2.5rem;
    }

    .experience-card {
        padding: 2rem;
    }

    .timeline-item {
        padding: 20px 20px 20px 40px;
    }

    .timeline-content {
        padding: 20px;
    }

    footer {
        padding: 2.5rem 1.8rem 2rem;
        border-radius: 24px;
        margin: 0 1rem 2rem;
    }

    header {
        top: 10px;
        width: 95%;
    }

    .contact-links {
        flex-direction: column;
        gap: 1.5rem;
        margin-bottom: 3rem;
    }
}

/* Small Mobile Responsive */
@media screen and (max-width: 480px) {
    .nav-links {
        width: 85%;
    }

    section.section {
        padding: 2.5rem 1.2rem;
        margin-bottom: 2.5rem;
        border-radius: 20px;
    }

    #hero {
        padding: 2.5rem 1.2rem;
        margin-top: 80px;
        margin-bottom: 2.5rem;
        border-radius: 20px;
    }

    .hero-content h1 {
        font-size: 2.2rem;
    }
    
    .hero-content h2 {
        font-size: 1.3rem;
    }

    .hero-image {
        width: 150px;
        height: 150px;
        margin-bottom: 1.5rem;
    }

    .section-title {
        font-size: 1.8rem;
        margin-bottom: 2rem;
    }

    .hero-badges {
        flex-direction: column;
        align-items: center;
    }

    .btn {
        display: block;
        width: 100%;
        margin-bottom: 1rem;
    }

    .btn.secondary {
        margin-left: 0;
    }

    .about-stats {
        grid-template-columns: 1fr 1fr;
    }

    .experience-card {
        padding: 1.5rem;
    }

    .timeline-content {
        padding: 1.5rem;
    }
    
    .skill-category {
        padding: 1.5rem;
    }

    .teaching-card {
        padding: 1.3rem 1.2rem;
    }

    .talk-card {
        flex-direction: column;
        padding: 1.5rem;
    }

    footer {
        padding: 2rem 1.2rem 1.5rem;
        margin: 0 0.8rem 1.5rem;
    }
}

/* Animations */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.fade-in.appear {
    opacity: 1;
    transform: translateY(0);
}