/* ========================================
   CSS Custom Properties (Variables)
   ======================================== */
:root {
    /* Colors */
    --color-bg: #FAFAFA;
    --color-surface: #FFFFFF;
    --color-text: #1A1A1A;
    --color-text-secondary: #5A5A5A;
    --color-accent: #2D5F8D;
    --color-accent-hover: #1E4468;
    --color-work: #2D5F8D;
    --color-education: #6B4B8D;
    --color-timeline-line: #D0D0D0;
    --color-border: #E0E0E0;
    --color-hover: #F5F5F5;
    --color-focus: #2D5F8D;
    --color-success: #2E7D32;
    --color-error: #C62828;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    
    /* Spacing */
    --spacing-1: 0.5rem;
    --spacing-2: 1rem;
    --spacing-3: 1.5rem;
    --spacing-4: 2rem;
    --spacing-5: 2.5rem;
    --spacing-6: 3rem;
    --spacing-8: 4rem;
    --spacing-10: 5rem;
    
    /* Layout */
    --max-width: 1200px;
    --border-radius: 8px;
    --transition-speed: 0.3s;
    
    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
}

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

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

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ========================================
   Typography
   ======================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: var(--font-weight-bold);
    line-height: var(--line-height-tight);
    margin-bottom: var(--spacing-2);
}

h1 { font-size: var(--font-size-5xl); }
h2 { font-size: var(--font-size-4xl); }
h3 { font-size: var(--font-size-2xl); }
h4 { font-size: var(--font-size-xl); }
h5 { font-size: var(--font-size-lg); }
h6 { font-size: var(--font-size-base); }

p {
    margin-bottom: var(--spacing-2);
}

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

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

a:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 2px;
    border-radius: 2px;
}

/* ========================================
   Accessibility - Skip Link
   ======================================== */
.skip-link {
    position: absolute;
    top: -100px;
    left: 0;
    background: var(--color-accent);
    color: white;
    padding: var(--spacing-2) var(--spacing-3);
    z-index: 9999;
    font-weight: var(--font-weight-semibold);
}

.skip-link:focus {
    top: 0;
}

/* ========================================
   Layout - Container
   ======================================== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-3);
}

.section {
    padding: var(--spacing-8) 0;
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-2);
    color: var(--color-text);
}

.section-description {
    text-align: center;
    color: var(--color-text-secondary);
    max-width: 600px;
    margin: 0 auto var(--spacing-6);
}

/* ========================================
   Header & Navigation
   ======================================== */
.header {
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-2) var(--spacing-3);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo .logo-text {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-text);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-4);
    align-items: center;
}

.nav-link {
    color: var(--color-text);
    font-weight: var(--font-weight-medium);
    padding: var(--spacing-1) var(--spacing-2);
    border-radius: var(--border-radius);
    transition: background-color var(--transition-speed) ease;
}

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

/* Hamburger Menu Button (Mobile) */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-1);
}

.hamburger {
    width: 25px;
    height: 3px;
    background-color: var(--color-text);
    transition: all var(--transition-speed) ease;
}

/* ========================================
   Hero/About Section
   ======================================== */
.hero-section {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    min-height: 80vh;
    display: flex;
    align-items: center;
}

.hero-content {
    display: flex;
    align-items: center;
    gap: var(--spacing-6);
    flex-wrap: wrap;
}

.hero-image {
    flex: 0 0 auto;
}

.profile-photo {
    width: 250px;
    height: 250px;
    border-radius: 50%;
    object-fit: cover;
    border: 5px solid var(--color-surface);
    box-shadow: var(--shadow-lg);
}

.hero-text {
    flex: 1;
    min-width: 300px;
}

.hero-title {
    margin-bottom: var(--spacing-1);
}

.hero-subtitle {
    font-size: var(--font-size-2xl);
    color: var(--color-accent);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-3);
}

.hero-description {
    font-size: var(--font-size-lg);
    line-height: var(--line-height-relaxed);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-4);
}

.hero-cta {
    display: flex;
    gap: var(--spacing-2);
    margin-bottom: var(--spacing-4);
    flex-wrap: wrap;
}

.social-links {
    display: flex;
    gap: var(--spacing-2);
}

.social-links a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background-color: var(--color-surface);
    color: var(--color-text);
    font-size: var(--font-size-xl);
    transition: all var(--transition-speed) ease;
    box-shadow: var(--shadow-sm);
}

.social-links a:hover {
    background-color: var(--color-accent);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

/* ========================================
   Buttons
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-1);
    padding: var(--spacing-2) var(--spacing-4);
    border-radius: var(--border-radius);
    font-weight: var(--font-weight-semibold);
    font-size: var(--font-size-base);
    border: 2px solid transparent;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    text-decoration: none;
}

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

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

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

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

/* ========================================
   Timeline Section (London Tube Map Style)
   ======================================== */
.timeline-section {
    background-color: var(--color-surface);
}

.timeline {
    position: relative;
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-4) 0;
}

.timeline-list {
    list-style: none;
    position: relative;
}

/* Central vertical line */
.timeline-list::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    bottom: 0;
    width: 3px;
    background-color: var(--color-timeline-line);
    transform: translateX(-50%);
}

.timeline-item {
    position: relative;
    margin-bottom: var(--spacing-8);
    display: grid;
    grid-template-columns: 1fr 60px 1fr;
    gap: var(--spacing-3);
    align-items: flex-start;
}

/* Alternate sides for date */
.timeline-item:nth-child(odd) .timeline-date {
    grid-column: 1;
    text-align: right;
}

.timeline-item:nth-child(even) .timeline-date {
    grid-column: 3;
    text-align: left;
}

.timeline-item:nth-child(odd) .timeline-content {
    grid-column: 3;
}

.timeline-item:nth-child(even) .timeline-content {
    grid-column: 1;
    grid-row: 1;
}

/* Timeline Date */
.timeline-date {
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-secondary);
    padding: var(--spacing-1) var(--spacing-2);
    background-color: var(--color-hover);
    border-radius: var(--border-radius);
    display: inline-block;
    white-space: nowrap;
}

/* Timeline Node (Central Circle) */
.timeline-node {
    grid-column: 2;
    display: flex;
    justify-content: center;
    position: relative;
    z-index: 2;
}

.timeline-icon {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--color-surface);
    border: 3px solid var(--color-timeline-line);
    font-size: var(--font-size-xl);
    transition: all var(--transition-speed) ease;
    box-shadow: var(--shadow-sm);
}

.work-icon {
    color: var(--color-work);
    border-color: var(--color-work);
}

.education-icon {
    color: var(--color-education);
    border-color: var(--color-education);
}

/* Timeline Content */
.timeline-content {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    padding: var(--spacing-3);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-speed) ease;
    cursor: pointer;
    border: 2px solid transparent;
}

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

.timeline-item {
    cursor: pointer !important;
    transition: all var(--transition-speed) ease;
    position: relative;
}

.timeline-item::after {
    content: '→';
    position: absolute;
    right: var(--spacing-4);
    top: 50%;
    transform: translateY(-50%);
    font-size: var(--font-size-2xl);
    color: var(--color-accent);
    opacity: 0;
    transition: all var(--transition-speed) ease;
}

.timeline-item:hover {
    transform: translateX(5px);
}

.timeline-item:hover::after {
    opacity: 1;
    right: var(--spacing-3);
}

.timeline-item:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 4px;
    border-radius: var(--border-radius);
}

.timeline-item * {
    cursor: pointer !important;
}

.timeline-title {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-1);
    position: relative;
}

.timeline-title::after {
    content: 'Click to view details';
    font-size: var(--font-size-xs);
    color: var(--color-accent);
    font-weight: var(--font-weight-medium);
    margin-top: var(--spacing-1);
    opacity: 0.7;
    font-style: italic;
}

.timeline-title h3 {
    color: var(--color-text);
    font-size: var(--font-size-xl);
    margin: 0;
    transition: color var(--transition-speed) ease;
}

.timeline-company {
    font-size: var(--font-size-base);
    color: var(--color-text-secondary);
    font-weight: var(--font-weight-medium);
}

/* Hover States */
.timeline-item:hover .timeline-icon {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

.timeline-item:hover .timeline-content {
    box-shadow: var(--shadow-md);
}

.timeline-item:hover .timeline-title h3 {
    color: var(--color-accent);
}

/* Timeline Details (for modal content) */
.timeline-details {
    margin-top: var(--spacing-3);
    padding-top: var(--spacing-3);
    border-top: 1px solid var(--color-border);
}

.timeline-meta {
    display: flex;
    gap: var(--spacing-3);
    flex-wrap: wrap;
    margin-bottom: var(--spacing-3);
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
}

.timeline-meta i {
    margin-right: var(--spacing-1);
}

.timeline-meta a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color var(--transition-speed) ease;
}

.timeline-meta a:hover {
    color: var(--color-accent-hover);
    text-decoration: underline;
}

.timeline-description h4 {
    font-size: var(--font-size-lg);
    margin-top: var(--spacing-3);
    margin-bottom: var(--spacing-2);
}

.timeline-description ul {
    padding-left: var(--spacing-3);
    margin-bottom: var(--spacing-3);
}

.timeline-description li {
    margin-bottom: var(--spacing-1);
    color: var(--color-text-secondary);
}

/* Tech Tags */
.tech-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-1);
    margin-bottom: var(--spacing-3);
}

.tag {
    padding: var(--spacing-1) var(--spacing-2);
    background-color: var(--color-hover);
    color: var(--color-text);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
}

/* Timeline Media */
.timeline-media {
    margin-top: var(--spacing-3);
}

.media-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-2);
    margin: var(--spacing-2) 0;
}

.media-item {
    aspect-ratio: 16/9;
    background-color: var(--color-hover);
    border-radius: var(--border-radius);
    overflow: hidden;
}

.media-item img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-1);
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: background-color var(--transition-speed) ease;
}

.video-placeholder:hover {
    background-color: var(--color-accent);
    color: white;
}

.external-link, .document-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-1);
    margin-right: var(--spacing-2);
    margin-top: var(--spacing-2);
    color: var(--color-accent);
    font-weight: var(--font-weight-medium);
}

/* ========================================
   Skills Section
   ======================================== */
.skills-section {
    background-color: var(--color-bg);
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-4);
}

.skill-category {
    background-color: var(--color-surface);
    padding: var(--spacing-4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.skill-category-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    margin-bottom: var(--spacing-3);
    font-size: var(--font-size-xl);
    color: var(--color-accent);
}

.skill-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-3);
}

.skill-item {
    width: 100%;
}

.skill-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-1);
}

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

.skill-level {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
}

.skill-bar {
    width: 100%;
    height: 8px;
    background-color: var(--color-border);
    border-radius: 10px;
    overflow: hidden;
}

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

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-1);
}

/* ========================================
   Projects Section
   ======================================== */
.projects-section {
    background-color: var(--color-surface);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: var(--spacing-4);
}

.project-card {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-speed) ease;
}

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

.project-image {
    position: relative;
    width: 100%;
    aspect-ratio: 16/9;
    overflow: hidden;
    background-color: var(--color-hover);
}

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

.project-card:hover .project-image img {
    transform: scale(1.05);
}

.project-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(45, 95, 141, 0.9);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity var(--transition-speed) ease;
}

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

.project-link {
    color: white;
    font-size: var(--font-size-3xl);
}

.project-content {
    padding: var(--spacing-4);
}

.project-title {
    font-size: var(--font-size-2xl);
    margin-bottom: var(--spacing-2);
}

.project-description {
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-3);
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-1);
    margin-bottom: var(--spacing-3);
}

.project-links {
    display: flex;
    gap: var(--spacing-2);
    flex-wrap: wrap;
    margin-bottom: var(--spacing-3);
}

.project-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-1);
    padding: var(--spacing-1) var(--spacing-3);
    background-color: var(--color-hover);
    color: var(--color-text);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    transition: all var(--transition-speed) ease;
}

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

/* Video Container (Responsive) */
.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
    overflow: hidden;
    margin-top: var(--spacing-3);
    border-radius: var(--border-radius);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border-radius: var(--border-radius);
}

/* ========================================
   Certifications Section
   ======================================== */
.certifications-section {
    background-color: var(--color-bg);
}

.certifications-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-4);
}

.certification-card {
    background-color: var(--color-surface);
    padding: var(--spacing-4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    display: flex;
    gap: var(--spacing-3);
    transition: all var(--transition-speed) ease;
}

.certification-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.certification-icon {
    font-size: var(--font-size-3xl);
    color: var(--color-accent);
    flex-shrink: 0;
}

.certification-content {
    flex: 1;
}

.certification-title {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-1);
}

.certification-issuer {
    color: var(--color-text-secondary);
    font-weight: var(--font-weight-medium);
    margin-bottom: var(--spacing-1);
}

.certification-date, .certification-id {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-1);
}

.certification-link {
    font-size: var(--font-size-sm);
    margin-top: var(--spacing-2);
}

.certification-link a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color var(--transition-speed) ease;
}

.certification-link a:hover {
    color: var(--color-accent-hover);
    text-decoration: underline;
}

.certification-links {
    display: flex;
    gap: var(--spacing-2);
    margin-top: var(--spacing-2);
}

.cert-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-1);
    padding: var(--spacing-1) var(--spacing-2);
    background-color: var(--color-hover);
    color: var(--color-accent);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    transition: all var(--transition-speed) ease;
}

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

/* ========================================
   Contact Section
   ======================================== */
.contact-section {
    background-color: var(--color-surface);
}

.contact-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: var(--spacing-6);
    max-width: 1000px;
    margin: 0 auto;
}

/* Contact Form */
.contact-form-wrapper {
    background-color: var(--color-surface);
    padding: var(--spacing-4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
}

.form-group {
    margin-bottom: var(--spacing-3);
}

.form-label {
    display: block;
    margin-bottom: var(--spacing-1);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text);
}

.required {
    color: var(--color-error);
}

.form-input, .form-textarea {
    width: 100%;
    padding: var(--spacing-2);
    border: 2px solid var(--color-border);
    border-radius: var(--border-radius);
    font-family: inherit;
    font-size: var(--font-size-base);
    transition: border-color var(--transition-speed) ease;
}

.form-input:focus, .form-textarea:focus {
    outline: none;
    border-color: var(--color-accent);
}

.form-input.error, .form-textarea.error {
    border-color: var(--color-error);
}

.form-error {
    display: block;
    color: var(--color-error);
    font-size: var(--font-size-sm);
    margin-top: var(--spacing-1);
}

.form-success {
    padding: var(--spacing-2);
    background-color: var(--color-success);
    color: white;
    border-radius: var(--border-radius);
    margin-top: var(--spacing-2);
    display: flex;
    align-items: center;
    gap: var(--spacing-1);
}

.btn-submit {
    width: 100%;
    justify-content: center;
}

/* Contact Info */
.contact-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
}

.contact-info-item {
    display: flex;
    gap: var(--spacing-2);
    align-items: flex-start;
}

.contact-info-item i {
    font-size: var(--font-size-2xl);
    color: var(--color-accent);
    flex-shrink: 0;
}

.contact-info-item h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-1);
}

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

/* ========================================
   Footer
   ======================================== */
.footer {
    background-color: var(--color-text);
    color: white;
    padding: var(--spacing-4) 0;
    margin-top: var(--spacing-8);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-3);
}

.footer-links {
    display: flex;
    gap: var(--spacing-3);
}

.footer-links a {
    color: white;
    opacity: 0.8;
    transition: opacity var(--transition-speed) ease;
}

.footer-links a:hover {
    opacity: 1;
}

/* ========================================
   Back to Top Button
   ======================================== */
.back-to-top {
    position: fixed;
    bottom: var(--spacing-4);
    right: var(--spacing-4);
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--color-accent);
    color: white;
    border: none;
    font-size: var(--font-size-xl);
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-speed) ease;
    z-index: 999;
    display: flex;
    align-items: center;
    justify-content: center;
}

.back-to-top:hover {
    background-color: var(--color-accent-hover);
    transform: translateY(-4px);
}

.back-to-top:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 2px;
}

/* ========================================
   Responsive Design - Mobile First
   ======================================== */

/* Mobile Styles (< 768px) - Default styles above */

@media (max-width: 767px) {
    /* Typography adjustments */
    h1 { font-size: var(--font-size-4xl); }
    h2 { font-size: var(--font-size-3xl); }
    
    /* Navigation - Mobile */
    .nav-toggle {
        display: flex;
    }
    
    .nav-menu {
        position: fixed;
        top: 72px;
        left: -100%;
        width: 80%;
        max-width: 300px;
        height: calc(100vh - 72px);
        background-color: var(--color-surface);
        flex-direction: column;
        align-items: flex-start;
        padding: var(--spacing-4);
        box-shadow: var(--shadow-lg);
        transition: left var(--transition-speed) ease;
        z-index: 999;
    }
    
    .nav-menu.active {
        left: 0;
    }
    
    .nav-link {
        width: 100%;
        padding: var(--spacing-2);
    }
    
    /* Hero Section */
    .hero-section {
        min-height: auto;
        padding: var(--spacing-6) 0;
    }
    
    .hero-content {
        flex-direction: column;
        text-align: center;
        gap: var(--spacing-4);
    }
    
    .profile-photo {
        width: 200px;
        height: 200px;
    }
    
    .hero-cta {
        justify-content: center;
    }
    
    .social-links {
        justify-content: center;
    }
    
    /* Timeline - Mobile Layout */
    .timeline-list::before {
        left: 30px;
    }
    
    .timeline-item {
        grid-template-columns: 60px 1fr;
        gap: var(--spacing-2);
        margin-bottom: var(--spacing-6);
    }
    
    .timeline-date {
        grid-column: 2;
        grid-row: 1;
        text-align: left;
        margin-bottom: var(--spacing-2);
    }
    
    .timeline-node {
        grid-column: 1;
        grid-row: 2;
        justify-content: flex-start;
    }
    
    .timeline-content {
        grid-column: 2;
        grid-row: 2;
    }
    
    .timeline-icon {
        width: 40px;
        height: 40px;
        font-size: var(--font-size-lg);
    }
    
    /* Contact Section */
    .contact-content {
        grid-template-columns: 1fr;
    }
    
    /* Projects Grid */
    .projects-grid {
        grid-template-columns: 1fr;
    }
}

/* Tablet Styles (768px - 1023px) */
@media (min-width: 768px) and (max-width: 1023px) {
    .container {
        padding: 0 var(--spacing-4);
    }
    
    .projects-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Desktop Styles (1024px+) */
@media (min-width: 1024px) {
    .section {
        padding: var(--spacing-10) 0;
    }
    
    h1 { font-size: var(--font-size-5xl); }
}

/* Large Desktop (1440px+) */
@media (min-width: 1440px) {
    .container {
        padding: 0 var(--spacing-6);
    }
}

/* ========================================
   Modal Styles - Rewritten from Scratch
   ======================================== */

/* Modal Base - Hidden by default */
.modal[hidden] {
    display: none !important;
}

.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100vw;
    height: 100vh;
    z-index: 9999;
    display: flex;
    align-items: flex-end;
    justify-content: center;
    animation: modalFadeIn 0.3s ease-out;
}

@keyframes modalFadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* Dark overlay behind modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.75);
    backdrop-filter: blur(3px);
    cursor: pointer;
}

/* Modal container with content */
.modal-container {
    position: relative;
    z-index: 10000;
    background-color: var(--color-surface);
    width: 100%;
    max-height: 75vh;
    border-radius: 16px 16px 0 0;
    box-shadow: 0 -4px 30px rgba(0, 0, 0, 0.3);
    display: flex;
    flex-direction: column;
    animation: modalSlideUp 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes modalSlideUp {
    from {
        transform: translateY(100%);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

/* Close button */
.modal-close {
    position: absolute;
    top: 12px;
    right: 12px;
    z-index: 10001;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 2px solid var(--color-border);
    background-color: var(--color-surface);
    color: var(--color-text);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    transition: all 0.2s ease;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.modal-close:hover {
    background-color: var(--color-accent);
    border-color: var(--color-accent);
    color: white;
    transform: rotate(90deg) scale(1.1);
}

.modal-close:active {
    transform: rotate(90deg) scale(0.95);
}

/* Modal content area */
.modal-content {
    padding: 56px 20px 20px 20px;
    overflow-y: auto;
    overflow-x: hidden;
    flex: 1;
    -webkit-overflow-scrolling: touch;
}

/* Modal header styling */
.modal-header {
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--color-border);
}

.modal-header h3 {
    font-size: 20px;
    font-weight: 700;
    color: var(--color-text);
    margin: 0 0 8px 0;
    line-height: 1.3;
    padding-right: 30px;
}

.modal-company {
    font-size: 14px;
    color: var(--color-text-secondary);
    font-weight: 500;
    display: block;
}

/* Modal body styling */
.modal-body {
    line-height: 1.6;
    color: var(--color-text);
    font-size: 15px;
}

.modal-body h4 {
    margin-top: 20px;
    margin-bottom: 10px;
    font-size: 16px;
    font-weight: 600;
    color: var(--color-text);
}

.modal-body ul {
    margin: 10px 0;
    padding-left: 20px;
}

.modal-body li {
    margin-bottom: 6px;
    font-size: 14px;
}

.modal-body p {
    margin-bottom: 12px;
    font-size: 14px;
}

/* Custom scrollbar */
.modal-content::-webkit-scrollbar {
    width: 8px;
}

.modal-content::-webkit-scrollbar-track {
    background: var(--color-hover);
}

.modal-content::-webkit-scrollbar-thumb {
    background: var(--color-accent);
    border-radius: 4px;
}

.modal-content::-webkit-scrollbar-thumb:hover {
    background: var(--color-accent-hover);
}

/* Extra small phones - Portrait */
@media (max-width: 374px) {
    .modal-container {
        max-height: 70vh;
        border-radius: 12px 12px 0 0;
    }
    
    .modal-close {
        top: 8px;
        right: 8px;
        width: 36px;
        height: 36px;
        font-size: 16px;
    }
    
    .modal-content {
        padding: 48px 16px 16px 16px;
    }
    
    .modal-header h3 {
        font-size: 18px;
        padding-right: 40px;
    }
    
    .modal-company {
        font-size: 13px;
    }
    
    .modal-body {
        font-size: 14px;
    }
    
    .modal-body h4 {
        font-size: 15px;
    }
    
    .modal-body li,
    .modal-body p {
        font-size: 13px;
    }
}

/* Small phones - Landscape and larger portraits */
@media (min-width: 375px) and (max-width: 767px) {
    .modal-container {
        max-height: 75vh;
    }
    
    .modal-content {
        padding: 56px 20px 20px 20px;
    }
}

/* Tablet and up */
@media (min-width: 768px) {
    .modal {
        align-items: center;
        padding: 24px;
    }
    
    .modal-container {
        width: 90%;
        max-width: 800px;
        max-height: 85vh;
        border-radius: 16px;
        animation: modalScaleIn 0.4s cubic-bezier(0.16, 1, 0.3, 1);
    }
    
    @keyframes modalScaleIn {
        from {
            transform: scale(0.9);
            opacity: 0;
        }
        to {
            transform: scale(1);
            opacity: 1;
        }
    }
    
    .modal-close {
        top: 20px;
        right: 20px;
        width: 48px;
        height: 48px;
        font-size: 24px;
    }
    
    .modal-content {
        padding: 70px 40px 40px 40px;
    }
    
    .modal-header {
        margin-bottom: 24px;
        padding-bottom: 16px;
    }
    
    .modal-header h3 {
        font-size: 28px;
        padding-right: 0;
    }
    
    .modal-company {
        font-size: 18px;
    }
    
    .modal-body {
        font-size: 16px;
        line-height: 1.7;
    }
    
    .modal-body h4 {
        font-size: 20px;
        margin-top: 24px;
        margin-bottom: 12px;
    }
    
    .modal-body ul {
        margin: 12px 0;
        padding-left: 24px;
    }
    
    .modal-body li,
    .modal-body p {
        font-size: 16px;
        margin-bottom: 8px;
    }
}

/* Desktop */
@media (min-width: 1024px) {
    .modal {
        padding: 32px;
    }
    
    .modal-container {
        width: 80%;
        max-width: 900px;
        max-height: 90vh;
    }
    
    .modal-content {
        padding: 80px 48px 48px 48px;
    }
    
    .modal-header h3 {
        font-size: 32px;
    }
}

/* ========================================
   Print Styles
   ======================================== */
@media print {
    .nav, .back-to-top, .hero-cta, .social-links, .modal {
        display: none;
    }
    
    body {
        background: white;
    }
    
    .section {
        page-break-inside: avoid;
    }
}