/* =====================================================
   Apple-Style Minimalist Portfolio
   ===================================================== */

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

:root {
    --primary-color: #000000;
    --secondary-color: #1d1d1f;
    --text-primary: #1d1d1f;
    --text-secondary: #6e6e73;
    --text-light: #f5f5f7;
    --background-white: #ffffff;
    --background-gray: #f5f5f7;
    --background-dark: #1d1d1f;
    --accent-color: #0071e3;
    --border-color: #d2d2d7;
    --shadow: 0 2px 16px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 4px 24px rgba(0, 0, 0, 0.12);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    color: var(--text-primary);
    background-color: var(--background-white);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    color: var(--text-primary);
}

h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
}

h2 {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 600;
}

h3 {
    font-size: clamp(1.25rem, 2.5vw, 1.75rem);
    font-weight: 600;
}

h4 {
    font-size: 1.125rem;
    font-weight: 600;
}

p {
    font-size: 1.0625rem;
    line-height: 1.7;
    color: var(--text-secondary);
}

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

a:hover {
    opacity: 0.7;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: var(--transition);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 48px;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2.5rem;
    align-items: center;
}

.nav-link {
    font-size: 0.875rem;
    color: var(--text-primary);
    font-weight: 400;
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-color);
    transition: width 0.3s ease;
}

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

/* Hamburger Menu Button */
.nav-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0;
    width: 24px;
    height: 20px;
    position: relative;
    z-index: 1001;
}

.nav-toggle span {
    display: block;
    width: 100%;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: all 0.3s ease;
    position: absolute;
}

.nav-toggle span:nth-child(1) {
    top: 0;
}

.nav-toggle span:nth-child(2) {
    top: 50%;
    transform: translateY(-50%);
}

.nav-toggle span:nth-child(3) {
    bottom: 0;
}

/* Hamburger animation when active */
.nav-toggle.active span:nth-child(1) {
    top: 50%;
    transform: translateY(-50%) rotate(45deg);
}

.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
    bottom: 50%;
    transform: translateY(50%) rotate(-45deg);
}

/* Hero Section */
.hero {
    padding: 120px 0 120px;
    text-align: center;
    scroll-margin-top: 0;
    position: relative;
    z-index: 1;
    min-height: calc(100vh - 48px);
    display: flex;
    align-items: center;
}

.hero-content {
    animation: fadeInUp 0.8s ease-out;
    max-width: 700px;
    margin: 0 auto;
}

.hero-image {
    width: 140px;
    height: 140px;
    margin: 0 auto 2rem;
    border-radius: 50%;
    overflow: hidden;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.12);
}

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

.hero-title {
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    font-weight: 400;
}

.hero-location {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.hero-links {
    display: flex;
    gap: 1.5rem;
    justify-content: center;
    flex-wrap: wrap;
}

.hero-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background: var(--background-white);
    border: 1px solid var(--border-color);
    border-radius: 980px;
    color: var(--text-primary);
    font-size: 0.9375rem;
    transition: var(--transition);
}

.hero-link:hover {
    background: var(--background-gray);
    transform: translateY(-2px);
    box-shadow: var(--shadow);
    opacity: 1;
}

.hero-link svg {
    opacity: 0.6;
}

/* Section */
.section {
    padding: 100px 0;
    scroll-margin-top: 48px; /* Navigation height */
    background: var(--background-white);
    position: relative;
    z-index: 2;
}

/* First section after hero */
#about {
    padding-top: 80px;
    scroll-margin-top: 48px;
}

.section-gray {
    background-color: var(--background-gray);
}

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

.section-dark .section-title {
    color: var(--text-light);
}

.section-dark .contact-text {
    color: rgba(245, 245, 247, 0.7);
}

.section-title {
    font-size: 2.5rem;
    margin-bottom: 3rem;
    text-align: center;
    letter-spacing: -0.02em;
}

.section-content {
    max-width: 720px;
    margin: 0 auto;
    text-align: center;
}

/* About */
.about-text {
    font-size: 1.125rem;
    line-height: 1.8;
    color: var(--text-secondary);
    text-align: center;
    max-width: 720px;
    margin: 0 auto;
}

/* Timeline */
.timeline {
    position: relative;
    max-width: 720px;
    margin: 0 auto;
}

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

.timeline-item {
    position: relative;
    padding-left: 3rem;
    padding-bottom: 3rem;
    animation: fadeInUp 0.6s ease-out;
}

.timeline-item:last-child {
    padding-bottom: 0;
}

.timeline-marker {
    position: absolute;
    left: -5px;
    top: 0;
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--accent-color);
    border: 2px solid var(--background-white);
    box-shadow: 0 0 0 4px var(--background-gray);
}

.timeline-content {
    background: var(--background-white);
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.timeline-content:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.75rem;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.timeline-header h3 {
    font-size: 1.25rem;
    color: var(--text-primary);
}

.timeline-date {
    font-size: 0.875rem;
    color: var(--text-secondary);
    white-space: nowrap;
}

.timeline-company {
    font-weight: 600;
    color: var(--accent-color);
    margin-bottom: 0.5rem;
}

.timeline-description {
    font-size: 1rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Awards */
.award-card {
    max-width: 480px;
    margin: 0 auto;
    padding: 2rem;
    background: var(--background-white);
    border-radius: 16px;
    box-shadow: var(--shadow);
    text-align: center;
    transition: var(--transition);
}

.award-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.award-card h3 {
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.award-event {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

/* Publications */
.publications-tabs {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 3rem;
    flex-wrap: wrap;
}

.tab-button {
    padding: 0.75rem 2rem;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: 980px;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.tab-button:hover {
    background: var(--background-white);
}

.tab-button.active {
    background: var(--text-primary);
    color: var(--background-white);
    border-color: var(--text-primary);
}

.tab-content {
    display: none;
    animation: fadeIn 0.4s ease-out;
}

.tab-content.active {
    display: block;
}

.publication-card {
    background: var(--background-white);
    padding: 2rem;
    margin-bottom: 1.5rem;
    border-radius: 16px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.publication-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.publication-title {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    line-height: 1.4;
    color: var(--text-primary);
}

.publication-authors {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    font-style: italic;
}

.publication-abstract {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

/* Grid Layout */
.grid-two {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 3rem;
}

/* Core Competencies */
.competencies-container {
    max-width: 900px;
    margin: 0 auto;
}

.competency-item {
    margin-bottom: 3rem;
    padding: 2rem;
    background: var(--background-white);
    border-radius: 16px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.competency-item:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.competency-title {
    font-size: 1.25rem;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    font-weight: 600;
}

.competency-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.competency-list li {
    padding: 0.75rem 0;
    padding-left: 1.75rem;
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.7;
    position: relative;
}

.competency-list li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--accent-color);
    font-weight: 600;
}

/* Education & Languages */
.education-languages-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.education-section,
.languages-section {
    min-width: 0;
    background: var(--background-white);
    border-radius: 20px;
    padding: 2.5rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.education-section:hover,
.languages-section:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.education-section .section-title,
.languages-section .section-title {
    font-size: 1.5rem;
    margin-bottom: 2rem;
    color: var(--text-primary);
    font-weight: 600;
}

.education-list {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.education-item {
    padding-bottom: 2rem;
    border-bottom: 1px solid rgba(0, 0, 0, 0.06);
}

.education-item:last-child {
    padding-bottom: 0;
    border-bottom: none;
}

.education-item h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.education-details {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

.languages-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.languages-list p {
    font-size: 1rem;
    color: var(--text-secondary);
    line-height: 1.8;
    padding: 0.5rem 0;
}

/* Legacy Education Grid (keeping for backwards compatibility) */
.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    max-width: 900px;
    margin: 0 auto;
}

/* Skills */
.skill-category {
    margin-bottom: 2.5rem;
}

.skill-category h4 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

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

.tag {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--background-white);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    font-size: 0.875rem;
    color: var(--text-secondary);
    transition: var(--transition);
}

.tag:hover {
    border-color: var(--accent-color);
    color: var(--accent-color);
}

/* Education */
.education-card {
    padding: 1.5rem;
    background: var(--background-white);
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
    transition: var(--transition);
}

.education-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.education-card h3 {
    margin-bottom: 0.5rem;
    font-size: 1.125rem;
}

.education-org {
    color: var(--accent-color);
    font-weight: 500;
    margin-bottom: 0.25rem;
}

.education-time {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.education-gpa {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Projects */
.project-card {
    background: var(--background-white);
    padding: 2rem;
    margin-bottom: 1.5rem;
    border-radius: 16px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.project-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.project-card h3 {
    margin-bottom: 0.5rem;
}

.project-role {
    color: var(--accent-color);
    font-weight: 500;
    margin-bottom: 1rem;
}

/* Certificates */
.certificates-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1rem;
}

.certificate-link {
    padding: 1.25rem;
    background: var(--background-white);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    font-size: 0.9375rem;
    color: var(--text-primary);
    transition: var(--transition);
    display: block;
}

.certificate-link:hover {
    border-color: var(--accent-color);
    box-shadow: var(--shadow);
    transform: translateY(-2px);
    opacity: 1;
}

/* Activities */
.activities-list {
    max-width: 720px;
    margin: 0 auto;
}

.activity-item {
    padding: 1rem 1.5rem;
    background: var(--background-white);
    border-left: 3px solid var(--accent-color);
    border-radius: 8px;
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.activity-item:hover {
    transform: translateX(8px);
    box-shadow: var(--shadow-hover);
}

.activity-item a {
    color: var(--text-primary);
    font-weight: 500;
}

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

/* Hobbies */
.hobbies-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1rem;
    max-width: 720px;
    margin: 0 auto;
}

.hobby-item {
    padding: 1.5rem;
    background: var(--background-gray);
    border-radius: 12px;
    text-align: center;
    font-size: 0.9375rem;
    color: var(--text-secondary);
    transition: var(--transition);
}

.hobby-item:hover {
    background: var(--background-white);
    box-shadow: var(--shadow);
    transform: translateY(-4px);
}

/* Contact */
.contact-content {
    text-align: center;
    max-width: 480px;
    margin: 0 auto;
}

.contact-text {
    font-size: 1.125rem;
    margin-bottom: 2rem;
}

/* Buttons */
.btn-link {
    display: inline-block;
    padding: 0.625rem 1.5rem;
    background: transparent;
    border: 1px solid var(--accent-color);
    border-radius: 980px;
    color: var(--accent-color);
    font-size: 0.9375rem;
    font-weight: 500;
    transition: var(--transition);
}

.btn-link:hover {
    background: var(--accent-color);
    color: var(--background-white);
    opacity: 1;
    transform: translateY(-2px);
}

.btn-primary {
    display: inline-block;
    padding: 1rem 2.5rem;
    background: var(--accent-color);
    border: none;
    border-radius: 980px;
    color: var(--background-white);
    font-size: 1.0625rem;
    font-weight: 500;
    transition: var(--transition);
}

.btn-primary:hover {
    background: #0077ed;
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0, 113, 227, 0.3);
    opacity: 1;
}

/* Footer */
.footer {
    padding: 2.5rem 0;
    text-align: center;
    background: var(--background-white);
    border-top: 1px solid var(--border-color);
}

.footer p {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

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

/* Responsive Design */
@media (max-width: 768px) {
    /* Show hamburger menu button */
    .nav-toggle {
        display: flex;
    }

    /* Mobile menu overlay */
    .nav-menu {
        position: fixed;
        top: 48px;
        left: 0;
        right: 0;
        background: rgba(255, 255, 255, 0.98);
        backdrop-filter: saturate(180%) blur(20px);
        -webkit-backdrop-filter: saturate(180%) blur(20px);
        flex-direction: column;
        gap: 0;
        padding: 2rem 0;
        max-height: 0;
        opacity: 0;
        visibility: hidden;
        transition: max-height 0.3s ease, opacity 0.3s ease, visibility 0.3s ease;
        overflow: hidden;
        z-index: 1002;
        box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
    }

    .nav-menu.active {
        max-height: calc(100vh - 48px);
        opacity: 1;
        visibility: visible;
        overflow-y: auto;
    }

    .nav-menu li {
        width: 100%;
        text-align: center;
        border-bottom: 1px solid var(--border-color);
    }

    .nav-link {
        display: block;
        padding: 1.25rem 2rem;
        font-size: 1.0625rem;
        font-weight: 500;
    }

    .nav-link::after {
        display: none;
    }

    .hero {
        padding: 100px 0 80px;
        scroll-margin-top: 0;
        min-height: calc(100vh - 48px);
    }

    .section {
        padding: 60px 0;
        scroll-margin-top: 48px;
    }

    #about {
        padding-top: 60px;
        scroll-margin-top: 48px;
    }

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

    .timeline::before {
        left: 0;
    }

    .timeline-item {
        padding-left: 2.5rem;
    }

    .timeline-header {
        flex-direction: column;
        align-items: flex-start;
    }

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

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

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

    .competency-item {
        padding: 1.5rem;
        margin-bottom: 2rem;
    }

    .competency-title {
        font-size: 1.125rem;
    }

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

    .education-languages-container {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .education-section,
    .languages-section {
        padding: 2rem;
    }

    .education-section .section-title,
    .languages-section .section-title {
        font-size: 1.375rem;
        margin-bottom: 1.5rem;
    }

    .education-list {
        gap: 1.5rem;
    }

    .education-item {
        padding-bottom: 1.5rem;
    }
}

@media (max-width: 480px) {
    .nav-container {
        padding: 0 1rem;
    }

    .nav-menu {
        gap: 0.75rem;
    }

    .hero-links {
        flex-direction: column;
        align-items: stretch;
    }

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

    .timeline-item {
        padding-left: 2rem;
    }

    .timeline-content {
        padding: 1rem;
    }

    .publication-card,
    .project-card {
        padding: 1.5rem;
    }
}

/* Print Styles */
@media print {
    .nav,
    .hero-links,
    .btn-link,
    .btn-primary {
        display: none;
    }

    .section {
        page-break-inside: avoid;
    }
}

/* Dark Mode Support (Optional) */
@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #ffffff;
        --secondary-color: #f5f5f7;
        --text-primary: #f5f5f7;
        --text-secondary: #a1a1a6;
        --text-light: #1d1d1f;
        --background-white: #000000;
        --background-gray: #1d1d1f;
        --background-dark: #f5f5f7;
        --border-color: #424245;
    }
}

/* Smooth Scrolling Enhancement */
@media (prefers-reduced-motion: no-preference) {
    html {
        scroll-behavior: smooth;
    }
}

/* Focus Styles for Accessibility */
a:focus,
button:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

/* Large Desktop Optimization */
@media (min-width: 1024px) {
    .nav-container {
        max-width: 1400px;
        padding: 0 3rem;
    }

    .container {
        max-width: 1400px;
        padding: 0 3rem;
    }

    .hero .container {
        max-width: 1400px;
    }

    .nav-menu {
        gap: 3rem;
    }

    .nav-link {
        font-size: 0.9375rem;
    }
}

/* Selection Styles */
::selection {
    background: var(--accent-color);
    color: var(--background-white);
}

::-moz-selection {
    background: var(--accent-color);
    color: var(--background-white);
}