/* 
=======================================
   BASE STYLES & VARIABLES
=======================================
*/
:root {
    /* Color Palette - Academic Blue & Clean Neutrals */
    --primary-color: #1a365d;
    /* Deep Academic Blue */
    --primary-light: #2c5282;
    /* Lighter Blue */
    --secondary-color: #718096;
    /* Slate Gray */
    --accent-color: #3182ce;
    /* Bright Blue Accent */

    --text-main: #2d3748;
    /* Dark slate for high readability */
    --text-light: #4a5568;
    /* Medium slate */
    --text-muted: #a0aec0;
    /* Light slate */

    --bg-main: #ffffff;
    /* Crisp white */
    --bg-light: #f7fafc;
    /* Very light bluish gray for sections */
    --bg-dark: #1a202c;
    /* Dark background for footer */

    --border-color: #e2e8f0;

    /* Typography */
    --font-main: 'Inter', system-ui, -apple-system, sans-serif;

    /* Layout */
    --max-width: 1100px;
    --section-padding: 80px 0;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);

    /* Transitions */
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    color: var(--text-main);
    background-color: var(--bg-main);
    line-height: 1.6;
    font-size: 16px;
    overflow-x: hidden;
}

h1,
h2,
h3,
h4,
h5,
h6 {
    font-weight: 700;
    color: var(--primary-color);
    line-height: 1.2;
    margin-bottom: 1rem;
}

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

a:hover {
    color: var(--primary-light);
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* 
=======================================
   UTILITY CLASSES
=======================================
*/
.container {
    width: 90%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

.section {
    padding: var(--section-padding);
}

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

.section-title {
    text-align: center;
    margin-bottom: 3rem;
}

.section-title h2 {
    font-size: 2.2rem;
    position: relative;
    display: inline-block;
}

.underline {
    width: 60px;
    height: 4px;
    background-color: var(--accent-color);
    margin: 0.5rem auto 1rem auto;
    border-radius: 2px;
}

.section-subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 4px;
    font-weight: 500;
    text-align: center;
    cursor: pointer;
    border: 2px solid transparent;
}

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

.btn-primary:hover {
    background-color: var(--primary-light);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

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

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

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

.btn-sm {
    padding: 0.4rem 1rem;
    font-size: 0.9rem;
}

/* Grids & Cards */
.grid {
    display: grid;
    gap: 2rem;
}

.card {
    background: var(--bg-main);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-5px);
}

/* 
=======================================
   HEADER & NAVIGATION
=======================================
*/
.header {
    background-color: rgba(255, 255, 255, 0.98);
    box-shadow: var(--shadow-sm);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    padding: 1rem 0;
    transition: var(--transition);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary-color);
    letter-spacing: -0.5px;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.logo-icon {
    width: 35px;
    height: 35px;
    border-radius: 50%;
    object-fit: contain;
}

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

.nav-link {
    color: var(--text-main);
    font-weight: 500;
    font-size: 0.95rem;
    position: relative;
    padding-bottom: 0.25rem;
}

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

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

.nav-link.active {
    color: var(--accent-color);
}

.mobile-nav-toggle {
    display: none;
    font-size: 1.5rem;
    color: var(--primary-color);
    background: transparent;
    border: none;
    cursor: pointer;
}

/* 
=======================================
   HOME / HERO
=======================================
*/
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 80px;
    /* Offset for sticky header */
    background: linear-gradient(135deg, #f7fafc 0%, #edf2f7 100%);
}

.hero-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 4rem;
}

.hero-content {
    flex: 1;
}

.greeting {
    color: var(--accent-color);
    font-weight: 600;
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.8rem;
    color: var(--secondary-color);
    font-weight: 500;
    margin-bottom: 1.5rem;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-light);
    margin-bottom: 2rem;
    max-width: 600px;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
}

.hero-image {
    flex: 1;
    max-width: 400px;
}

.hero-image img {
    border-radius: 50%;
    box-shadow: var(--shadow-lg);
    border: 8px solid white;
    aspect-ratio: 1/1;
    object-fit: cover;
}

.hero-social {
    display: flex;
    gap: 1.2rem;
}

.hero-social a {
    color: var(--primary-color);
    background-color: white;
    width: 45px;
    height: 45px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-size: 1.2rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.hero-social a:hover {
    background-color: var(--accent-color);
    color: white;
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--accent-color);
}

/* 
=======================================
   ABOUT ME
=======================================
*/
/* 
=======================================
   RESUME / CV SECTIONS
=======================================
*/
.resume-section {
    margin-bottom: 4rem;
}

.resume-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 1.5rem;
    margin-bottom: 2rem;
    gap: 2rem;
}

.resume-bio {
    flex: 1;
}

.resume-bio h2 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.resume-tagline {
    font-size: 1.2rem;
    color: var(--secondary-color);
    font-weight: 500;
    margin-bottom: 1rem;
}

.resume-download {
    flex-shrink: 0;
}

.resume-item {
    margin-bottom: 2rem;
    display: grid;
    grid-template-columns: 160px 1fr;
    gap: 1.5rem;
}

.resume-date {
    font-weight: 700;
    color: var(--primary-color);
    font-size: 1rem;
    text-align: right;
    padding-top: 0.2rem;
}

.resume-content {
    border-left: 2px solid var(--border-color);
    padding-left: 1.5rem;
    position: relative;
}

.resume-content::before {
    content: '';
    position: absolute;
    width: 10px;
    height: 10px;
    background-color: var(--accent-color);
    border-radius: 50%;
    left: -6px;
    top: 8px;
}

.resume-item h3 {
    margin: 0;
    font-size: 1.25rem;
    line-height: 1.2;
}

.resume-org {
    display: block;
    color: var(--accent-color);
    font-weight: 600;
    margin-bottom: 0.5rem;
    font-size: 1rem;
}

.resume-content p {
    color: var(--text-light);
    margin-bottom: 0.5rem;
}

/* Research Row View */
.research-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.research-list-item {
    background: white;
    padding: 1.5rem;
    border-radius: 4px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

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

.research-list-item h4 {
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.research-list-item p {
    color: var(--text-light);
    font-size: 0.95rem;
    margin-bottom: 0;
}

@media (max-width: 768px) {
    .resume-header {
        flex-direction: column;
        align-items: center;
        text-align: center;
    }

    .resume-item {
        grid-template-columns: 1fr;
        gap: 0.5rem;
    }

    .resume-date {
        text-align: left;
        padding-bottom: 0.5rem;
    }

    .resume-content {
        padding-left: 1rem;
    }
}

/* 
=======================================
   COURSES
=======================================
*/
.courses-grid {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.card-icon {
    font-size: 2rem;
    color: var(--accent-color);
    margin-bottom: 1rem;
}

.course-card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.25rem;
}

.course-level {
    color: var(--secondary-color);
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.course-card p {
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

.text-link {
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.text-link:hover {
    gap: 0.75rem;
    /* slight movement on hover */
}

/* 
=======================================
   RESEARCH
=======================================
*/
.research-content {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.research-item {
    text-align: center;
    padding: 2rem;
    background: white;
    border-radius: 8px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.research-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.research-icon {
    font-size: 3rem;
    color: var(--primary-light);
    margin-bottom: 1.5rem;
}

.research-item h3 {
    margin-bottom: 1rem;
}

.research-item p {
    color: var(--text-light);
}

/* 
=======================================
   PROJECTS
=======================================
*/
.projects-grid {
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
}

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

.tag {
    background: var(--bg-light);
    color: var(--primary-color);
    padding: 0.2rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    border: 1px solid var(--border-color);
}

.project-card h3 {
    margin-bottom: 0.75rem;
}

.project-card p {
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

/* 
=======================================
   PUBLICATIONS
=======================================
*/
.publications-list {
    max-width: 1200;
    margin: 0 auto;
}

.publication-item {
    display: flex;
    gap: 1rem;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.publication-item:last-child {
    border-bottom: none;
}

.pub-year {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--secondary-color);
    min-width: 80px;
}

.pub-title {
    font-size: 1.2rem;
    margin-bottom: 0.2rem;
    color: var(--primary-color);
}

.pub-authors {
    color: var(--text-main);
    margin-bottom: 0.25rem;
}

.pub-venue {
    color: var(--text-light);
    margin-bottom: 0.5rem;
}

.pub-links {
    display: flex;
    gap: 1rem;
}

.pub-link {
    font-size: 0.9rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

/* 
=======================================
   FOOTER
=======================================
*/
.footer {
    background-color: var(--bg-dark);
    color: var(--bg-light);
    padding: 4rem 0 0 0;
}

.footer-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-info h3 {
    color: white;
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.footer-info p,
.footer-contact p {
    color: var(--text-muted);
}

.footer-contact p {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.footer-social {
    display: flex;
    gap: 1rem;
}

.footer-social a {
    color: var(--bg-light);
    background-color: rgba(255, 255, 255, 0.1);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: var(--transition);
}

.footer-social a:hover {
    background-color: var(--accent-color);
    color: white;
    transform: translateY(-3px);
}

.footer-bottom {
    background-color: rgba(0, 0, 0, 0.2);
    padding: 1.5rem 0;
    text-align: center;
    color: var(--text-muted);
}

.small-text {
    font-size: 0.85rem;
    margin-top: 0.5rem;
}

/* 
=======================================
   MEDIA QUERIES (RESPONSIVE)
=======================================
*/
@media (max-width: 900px) {
    .hero-container {
        flex-direction: column-reverse;
        text-align: center;
        padding-top: 2rem;
    }

    .hero-description {
        margin: 0 auto 2rem auto;
    }

    .hero-buttons {
        justify-content: center;
    }

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

    .pub-year {
        font-size: 1.2rem;
    }
}

@media (max-width: 768px) {
    .header-container {
        position: relative;
    }

    .mobile-nav-toggle {
        display: block;
    }

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        width: 100%;
        background-color: white;
        padding: 1rem 0;
        box-shadow: var(--shadow-md);
        clip-path: polygon(0 0, 100% 0, 100% 0, 0 0);
        /* Hidden state */
        transition: clip-path 0.4s ease-in-out;
    }

    .nav-menu.active {
        clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
        /* Visible state */
    }

    .nav-list {
        flex-direction: column;
        align-items: center;
        gap: 1.5rem;
    }

    .hero-title {
        font-size: 2.8rem;
    }

    .hero-subtitle {
        font-size: 1.4rem;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2.2rem;
    }

    .hero-buttons {
        flex-direction: column;
        width: 100%;
    }

    .btn {
        width: 100%;
    }
}

/* 
=======================================
   TIMELINE LIST VIEW
=======================================
*/
.timeline-container {
    max-width: 1200px;
    margin: 0 auto;
    position: relative;
    padding-left: 2rem;
}

.timeline-container::before {
    content: '';
    position: absolute;
    left: 7px;
    top: 0;
    bottom: 0;
    width: 2px;
    background-color: var(--border-color);
}

.timeline-year {
    margin-bottom: 1.5rem;
    position: relative;
}

.timeline-year h3 {
    font-size: 1.8rem;
    color: var(--primary-color);
    margin-bottom: 0.75rem;
    background: var(--bg-main);
    display: inline-block;
    padding-right: 1rem;
    position: relative;
    z-index: 1;
}

.timeline-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.timeline-item {
    position: relative;
    padding-left: 1.5rem;
}

.timeline-dot {
    position: absolute;
    left: -29.5px;
    top: 8px;
    width: 14px;
    height: 14px;
    background-color: var(--accent-color);
    border-radius: 50%;
    border: 3px solid white;
    box-shadow: 0 0 0 2px var(--accent-color);
    z-index: 2;
}

.timeline-content {
    background: white;
    padding: 0.8rem 2rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.timeline-content:hover {
    transform: translateX(10px);
    border-color: var(--accent-color);
    box-shadow: var(--shadow-md);
}

.timeline-content h4:last-child {
    margin-bottom: 0;
}

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

.timeline-content p {
    color: var(--text-light);
    margin-bottom: 1rem;
}

.timeline-content p:last-child {
    margin-bottom: 0;
}

@media (max-width: 768px) {
    .timeline-container {
        padding-left: 1.5rem;
    }

    .timeline-container::before {
        left: 5px;
    }

    .timeline-dot {
        left: -19px;
        width: 10px;
        height: 10px;
    }

    .timeline-content:hover {
        transform: none;
    }
}

/* 
=======================================
   RESEARCH LIST VIEW
=======================================
*/
.research-list-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.research-list-item {
    background: white;
    padding: 0.8rem 1.2rem;
    border-radius: 8px;
    border-left: 5px solid var(--accent-color);
    box-shadow: var(--shadow-sm);
    display: flex;
    gap: 0.25rem;
    align-items: flex-start;
    transition: var(--transition);
}

.research-list-item:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-left-color: var(--primary-color);
}

.research-meta {
    min-width: 120px;
}

.research-year {
    font-weight: 700;
    color: var(--secondary-color);
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.research-details {
    flex: 1;
}

.research-title {
    font-size: 1.3rem;
    margin-bottom: 0.1rem;
    color: var(--primary-color);
}

.research-info {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    align-items: center;
}

.research-role,
.research-leader {
    font-size: 0.95rem;
    margin-bottom: 0;
    color: var(--text-light);
}

.research-role strong,
.research-leader strong {
    color: var(--text-main);
}

@media (max-width: 768px) {
    .research-list-item {
        flex-direction: column;
        gap: 0.5rem;
        padding: 1.5rem;
    }

    .research-meta {
        min-width: auto;
    }
}
/* 
=======================================
   404 ERROR PAGE
=======================================
*/
.error-404 {
    min-height: calc(100vh - 200px);
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 100px 0;
}

.error-404-content {
    max-width: 600px;
    margin: 0 auto;
}

.error-code {
    font-size: 8rem;
    font-weight: 900;
    color: var(--accent-color);
    line-height: 1;
    margin-bottom: 1rem;
    opacity: 0.2;
}

.error-404 h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.error-404 p {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 2rem;
}