/* ===================================
   CSS Reset and Base Styles
   =================================== */

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

:root {
    /* Color Palette - Professional Black/Gray Theme */
    --primary-black: #1a1a1a;
    --secondary-black: #2d2d2d;
    --near-black: #0a0a0a;
    --accent-blue: #4a9eff;
    --light-gray: #f5f5f5;
    --text-light: #e0e0e0;
    --text-dark: #1a1a1a;
    --border-gray: #404040;
    --medium-gray: #666;

    /* Typography */
    --font-heading: 'Roboto', sans-serif;
    --font-body: 'Open Sans', sans-serif;

    /* Spacing */
    --section-padding: 80px 20px;
    --container-max-width: 1200px;

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    line-height: 1.6;
    color: var(--text-dark);
    overflow-x: hidden;
}

.container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* ===================================
   Navigation Bar
   =================================== */

.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background-color: var(--primary-black);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    z-index: 1000;
    transition: var(--transition);
}

.nav-container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-light);
    text-decoration: none;
    font-family: var(--font-heading);
    letter-spacing: 1px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 30px;
}

.nav-link {
    color: var(--text-light);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
    padding: 5px 0;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--accent-blue);
    transition: width 0.3s ease;
}

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

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

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

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

/* ===================================
   Hero Section
   =================================== */

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--near-black) 0%, var(--secondary-black) 100%);
    color: var(--text-light);
    text-align: center;
    padding: 100px 20px 60px;
}

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

.hero-title {
    font-family: var(--font-heading);
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 15px;
    letter-spacing: 1px;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--accent-blue);
    margin-bottom: 15px;
    font-weight: 500;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-light);
    margin-bottom: 40px;
    opacity: 0.9;
}

.hero-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
    margin-bottom: 40px;
}

.btn {
    padding: 14px 32px;
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    border-radius: 5px;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-primary {
    background-color: var(--accent-blue);
    color: white;
    border: 2px solid var(--accent-blue);
}

.btn-primary:hover {
    background-color: transparent;
    color: var(--accent-blue);
}

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

.btn-secondary:hover {
    background-color: var(--text-light);
    color: var(--primary-black);
}

.social-links {
    display: flex;
    gap: 25px;
    justify-content: center;
}

.social-links a {
    color: var(--text-light);
    font-size: 1.8rem;
    transition: var(--transition);
}

.social-links a:hover {
    color: var(--accent-blue);
    transform: translateY(-3px);
}

/* ===================================
   Section Styles
   =================================== */

.section-dark {
    background-color: var(--primary-black);
    color: var(--text-light);
    padding: var(--section-padding);
}

.section-light {
    background-color: var(--light-gray);
    color: var(--text-dark);
    padding: var(--section-padding);
}

.section-title {
    font-family: var(--font-heading);
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 50px;
    position: relative;
    padding-bottom: 15px;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 3px;
    background-color: var(--accent-blue);
}

/* ===================================
   About Section
   =================================== */

.about-content {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 50px;
    align-items: start;
}

.about-image {
    text-align: center;
}

.about-image img {
    width: 100%;
    max-width: 300px;
    border-radius: 10px;
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.2);
}

.about-text p {
    margin-bottom: 20px;
    line-height: 1.8;
    font-size: 1.05rem;
}

.about-text h3 {
    margin-top: 30px;
    margin-bottom: 15px;
    color: var(--accent-blue);
    font-size: 1.3rem;
}

.research-interests {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 15px;
}

.research-interests li {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.05rem;
}

.research-interests i {
    color: var(--accent-blue);
    font-size: 1.2rem;
}

/* ===================================
   Education Section
   =================================== */

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

.education-item {
    background-color: var(--secondary-black);
    padding: 30px;
    border-radius: 10px;
    margin-bottom: 30px;
    border-left: 4px solid var(--accent-blue);
    transition: var(--transition);
}

.education-item:hover {
    transform: translateX(10px);
    box-shadow: 0 5px 20px rgba(74, 158, 255, 0.2);
}

.education-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 10px;
    flex-wrap: wrap;
    gap: 10px;
}

.education-item h3 {
    font-size: 1.4rem;
    color: var(--accent-blue);
    margin-bottom: 5px;
}

.education-item h4 {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 10px;
}

.education-date {
    color: var(--medium-gray);
    font-size: 0.95rem;
    font-weight: 600;
}

.education-focus {
    color: var(--text-light);
    font-style: italic;
    margin-bottom: 5px;
}

.education-location {
    color: var(--medium-gray);
    margin-bottom: 15px;
}

.education-stats {
    display: flex;
    gap: 30px;
    margin: 20px 0;
}

.stat {
    display: flex;
    gap: 8px;
}

.stat-label {
    color: var(--medium-gray);
    font-weight: 600;
}

.stat-value {
    color: var(--accent-blue);
    font-weight: 700;
}

.coursework {
    margin-top: 20px;
}

.coursework h5 {
    color: var(--accent-blue);
    margin-bottom: 10px;
    font-size: 1.1rem;
}

.coursework ul {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.coursework li {
    color: var(--text-light);
    padding-left: 20px;
    position: relative;
}

.coursework li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--accent-blue);
}

/* ===================================
   Publications Section
   =================================== */

.publications-list {
    max-width: 900px;
    margin: 0 auto;
}

.publication-item {
    display: flex;
    gap: 20px;
    background-color: white;
    padding: 25px;
    border-radius: 10px;
    margin-bottom: 25px;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
}

.publication-item:hover {
    box-shadow: 0 5px 20px rgba(74, 158, 255, 0.3);
    transform: translateY(-3px);
}

.publication-icon {
    font-size: 2rem;
    color: var(--accent-blue);
}

.publication-content h3 {
    font-size: 1.2rem;
    color: var(--primary-black);
    margin-bottom: 10px;
    line-height: 1.4;
}

.publication-authors {
    color: var(--medium-gray);
    margin-bottom: 5px;
    font-size: 0.95rem;
}

.publication-venue {
    color: var(--accent-blue);
    font-weight: 600;
    font-size: 0.95rem;
}

/* ===================================
   Projects Section
   =================================== */

.projects-grid {
    display: flex;
    flex-direction: column;
    gap: 40px;
    max-width: 900px;
    margin: 0 auto;
}

.project-card {
    background-color: var(--secondary-black);
    padding: 30px;
    border-radius: 10px;
    transition: var(--transition);
    border: 1px solid var(--border-gray);
}

.project-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(74, 158, 255, 0.2);
    border-color: var(--accent-blue);
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 10px;
    gap: 15px;
}

.project-card h3 {
    font-size: 1.4rem;
    color: var(--accent-blue);
    margin-bottom: 8px;
}

.project-date {
    color: var(--medium-gray);
    font-size: 0.9rem;
    white-space: nowrap;
}

.project-subtitle {
    color: var(--text-light);
    font-style: italic;
    margin-bottom: 15px;
    font-size: 0.95rem;
}

.project-description {
    color: var(--text-light);
    margin-bottom: 20px;
    line-height: 1.7;
}

.project-achievements h4 {
    color: var(--accent-blue);
    margin-bottom: 10px;
    font-size: 1.1rem;
}

.project-achievements ul {
    list-style: none;
    margin-bottom: 20px;
}

.project-achievements li {
    color: var(--text-light);
    padding-left: 20px;
    position: relative;
    margin-bottom: 8px;
}

.project-achievements li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--accent-blue);
    font-weight: bold;
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 20px;
}

.tech-tag {
    background-color: var(--primary-black);
    color: var(--accent-blue);
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.85rem;
    border: 1px solid var(--accent-blue);
}

.project-links {
    margin-top: 20px;
}

.project-link {
    color: var(--accent-blue);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-weight: 600;
    transition: var(--transition);
}

.project-link:hover {
    color: var(--text-light);
    gap: 12px;
}

/* Project Images */
.project-images {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    margin: 25px 0;
}

.project-image {
    text-align: center;
}

.project-image img {
    width: 100%;
    height: 350px;
    object-fit: contain;
    border-radius: 8px;
    border: 1px solid var(--border-gray);
    transition: var(--transition);
    background-color: rgba(255, 255, 255, 0.02);
}

.project-image img:hover {
    transform: scale(1.02);
    border-color: var(--accent-blue);
}

.image-caption {
    margin-top: 10px;
    font-size: 0.9rem;
    color: var(--text-light);
    font-style: italic;
}

/* ===================================
   Skills Section
   =================================== */

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.skill-category {
    background-color: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
    text-align: center;
}

.skill-category:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 20px rgba(74, 158, 255, 0.2);
}

.skill-icon {
    font-size: 3rem;
    color: var(--accent-blue);
    margin-bottom: 20px;
}

.skill-category h3 {
    color: var(--primary-black);
    margin-bottom: 20px;
    font-size: 1.3rem;
}

.skill-category ul {
    list-style: none;
    text-align: left;
}

.skill-category li {
    color: var(--text-dark);
    padding: 8px 0;
    padding-left: 25px;
    position: relative;
    border-bottom: 1px solid #e0e0e0;
}

.skill-category li:last-child {
    border-bottom: none;
}

.skill-category li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--accent-blue);
}

/* ===================================
   Experience Section
   =================================== */

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

.experience-item {
    background-color: var(--secondary-black);
    padding: 30px;
    border-radius: 10px;
    margin-bottom: 30px;
    border-left: 4px solid var(--accent-blue);
}

.experience-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 20px;
    flex-wrap: wrap;
    gap: 15px;
}

.experience-item h3 {
    font-size: 1.4rem;
    color: var(--accent-blue);
    margin-bottom: 5px;
}

.experience-item h4 {
    font-size: 1.1rem;
    color: var(--text-light);
}

.experience-date {
    color: var(--medium-gray);
    font-size: 0.95rem;
    font-weight: 600;
}

.experience-description p {
    color: var(--text-light);
    margin-bottom: 15px;
    line-height: 1.7;
}

.experience-description h5 {
    color: var(--accent-blue);
    margin-bottom: 10px;
    margin-top: 15px;
}

.experience-description ul {
    list-style: none;
}

.experience-description li {
    color: var(--text-light);
    padding-left: 20px;
    position: relative;
    margin-bottom: 8px;
}

.experience-description li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--accent-blue);
}

/* ===================================
   Contact Section
   =================================== */

.contact-intro {
    text-align: center;
    font-size: 1.1rem;
    margin-bottom: 50px;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-bottom: 50px;
}

.contact-item {
    background-color: white;
    padding: 30px;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
}

.contact-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 20px rgba(74, 158, 255, 0.2);
}

.contact-icon {
    font-size: 2.5rem;
    color: var(--accent-blue);
    margin-bottom: 15px;
}

.contact-item h3 {
    color: var(--primary-black);
    margin-bottom: 10px;
    font-size: 1.2rem;
}

.contact-item a {
    color: var(--accent-blue);
    text-decoration: none;
    transition: var(--transition);
}

.contact-item a:hover {
    color: var(--primary-black);
}

.contact-item p {
    color: var(--medium-gray);
}

.contact-cta {
    text-align: center;
}

/* ===================================
   Footer
   =================================== */

.footer {
    background-color: var(--near-black);
    color: var(--text-light);
    text-align: center;
    padding: 30px 20px;
}

.footer p {
    margin: 5px 0;
    opacity: 0.8;
}

/* ===================================
   Scroll to Top Button
   =================================== */

.scroll-top-btn {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background-color: var(--accent-blue);
    color: white;
    border: none;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    font-size: 1.2rem;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.3);
    z-index: 999;
}

.scroll-top-btn.visible {
    opacity: 1;
    visibility: visible;
}

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

/* ===================================
   Responsive Design
   =================================== */

@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--primary-black);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: 0 10px 27px rgba(0, 0, 0, 0.3);
        padding: 20px 0;
        gap: 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-menu li {
        margin: 15px 0;
    }

    .hero-title {
        font-size: 2.5rem;
    }

    .hero-subtitle {
        font-size: 1.2rem;
    }

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

    .about-content {
        grid-template-columns: 1fr;
        gap: 30px;
    }

    .research-interests {
        grid-template-columns: 1fr;
    }

    .coursework ul {
        grid-template-columns: 1fr;
    }

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

    .project-images {
        grid-template-columns: 1fr;
    }

    .project-image img {
        height: 250px;
    }

    .education-header,
    .experience-header,
    .project-header {
        flex-direction: column;
        align-items: start;
    }

    .education-stats {
        flex-direction: column;
        gap: 10px;
    }

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

    :root {
        --section-padding: 60px 20px;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .btn {
        padding: 12px 24px;
        font-size: 0.9rem;
    }

    .contact-grid,
    .skills-grid {
        grid-template-columns: 1fr;
    }
}