/* ===========================
   CSS Variables & Reset
   =========================== */

:root {
    /* Light Theme Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #e9ecef;
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --text-tertiary: #718096;
    --accent-primary: #2563eb;
    --accent-hover: #1e40af;
    --accent-light: #dbeafe;
    --border-color: #e2e8f0;
    --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);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    /* Dark Theme Colors */
    --bg-primary: #1a202c;
    --bg-secondary: #2d3748;
    --bg-tertiary: #4a5568;
    --text-primary: #f7fafc;
    --text-secondary: #e2e8f0;
    --text-tertiary: #cbd5e0;
    --accent-primary: #3b82f6;
    --accent-hover: #60a5fa;
    --accent-light: #1e3a8a;
    --border-color: #4a5568;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.4);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    transition: var(--transition);
}

/* ===========================
   Typography
   =========================== */

h1, h2, h3, h4, h5, h6 {
    line-height: 1.2;
    font-weight: 600;
    margin-bottom: 1rem;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.5rem; }
h3 { font-size: 1.75rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: 1rem;
}

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

/* ===========================
   Layout
   =========================== */

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

section {
    padding: 5rem 0;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--text-primary);
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: var(--accent-primary);
    margin: 1rem auto 0;
    border-radius: 2px;
}

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

.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
    transition: var(--transition);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-link {
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-primary);
    transition: width 0.3s ease;
}

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

.theme-toggle {
    background: var(--bg-secondary);
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    cursor: pointer;
    font-size: 1.2rem;
    transition: var(--transition);
    margin-left: 2rem;
}

.theme-toggle:hover {
    background: var(--bg-tertiary);
    transform: scale(1.1);
}

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

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    padding-top: 80px;
}

.hero-container {
    text-align: center;
}

.hero-greeting {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.hero-name {
    font-size: 4rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.hero-title {
    font-size: 2rem;
    color: var(--accent-primary);
    font-weight: 600;
    margin-bottom: 1rem;
}

.hero-tagline {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 3rem;
}

.btn {
    padding: 0.875rem 2rem;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 1rem;
    transition: var(--transition);
    display: inline-block;
    border: 2px solid transparent;
}

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

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

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

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

.hero-stats {
    display: flex;
    gap: 3rem;
    justify-content: center;
    margin-top: 3rem;
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent-primary);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-align: center;
}

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

.about {
    background: var(--bg-secondary);
}

.about-content {
    max-width: 900px;
    margin: 0 auto;
}

.about-text p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.8;
}

.about-highlights {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.highlight-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--bg-primary);
    border-radius: 0.5rem;
    box-shadow: var(--shadow-sm);
}

.highlight-icon {
    font-size: 2rem;
}

.highlight-text {
    font-size: 0.975rem;
    font-weight: 500;
    color: var(--text-primary);
}

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

.skills {
    background: var(--bg-primary);
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.skill-category {
    padding: 2rem;
    background: var(--bg-secondary);
    border-radius: 0.75rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

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

.skill-category-title {
    font-size: 1.25rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.skill-tag {
    padding: 0.5rem 1rem;
    background: var(--accent-light);
    color: var(--accent-primary);
    border-radius: 0.375rem;
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition);
}

[data-theme="dark"] .skill-tag {
    background: var(--accent-light);
    color: var(--accent-hover);
}

.skill-tag:hover {
    transform: scale(1.05);
}

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

.experience {
    background: var(--bg-secondary);
}

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

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

.timeline-item {
    position: relative;
    padding-left: 60px;
    margin-bottom: 3rem;
}

.timeline-marker {
    position: absolute;
    left: 11px;
    top: 0;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--accent-primary);
    border: 4px solid var(--bg-secondary);
}

.timeline-content {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.timeline-content:hover {
    transform: translateX(10px);
    box-shadow: var(--shadow-lg);
}

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

.timeline-title {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin: 0;
}

.timeline-company {
    font-size: 1.125rem;
    color: var(--accent-primary);
    font-weight: 600;
}

.timeline-date {
    font-size: 0.975rem;
    color: var(--text-tertiary);
    margin-bottom: 1rem;
}

.timeline-list {
    list-style: none;
    padding-left: 0;
}

.timeline-list li {
    position: relative;
    padding-left: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.timeline-list li::before {
    content: '▹';
    position: absolute;
    left: 0;
    color: var(--accent-primary);
    font-weight: bold;
}

.timeline-list li strong {
    color: var(--accent-primary);
    font-weight: 600;
}

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

.projects {
    background: var(--bg-primary);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.project-card {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

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

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.project-title {
    font-size: 1.25rem;
    color: var(--text-primary);
    margin: 0;
}

.project-type {
    padding: 0.25rem 0.75rem;
    background: var(--accent-light);
    color: var(--accent-primary);
    border-radius: 0.25rem;
    font-size: 0.75rem;
    font-weight: 600;
}

.project-description {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.tech-tag {
    padding: 0.375rem 0.75rem;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border-radius: 0.25rem;
    font-size: 0.825rem;
    font-weight: 500;
}

.project-link {
    color: var(--accent-primary);
    font-weight: 600;
    transition: var(--transition);
}

.project-link:hover {
    color: var(--accent-hover);
    transform: translateX(5px);
}

.project-link-disabled {
    color: var(--text-tertiary);
    font-size: 0.875rem;
    font-style: italic;
}

/* ===========================
   Philosophy Section
   =========================== */

.philosophy {
    background: var(--bg-secondary);
}

.philosophy-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.philosophy-card {
    background: var(--bg-primary);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    text-align: center;
}

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

.philosophy-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.philosophy-card h3 {
    font-size: 1.25rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.philosophy-card p {
    color: var(--text-secondary);
    line-height: 1.6;
    margin: 0;
}

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

.education {
    background: var(--bg-primary);
}

.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.education-card {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    text-align: center;
}

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

.education-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.education-card h3 {
    font-size: 1.125rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.education-institution {
    color: var(--accent-primary);
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.education-date {
    color: var(--text-tertiary);
    font-size: 0.875rem;
}

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

.contact {
    background: var(--bg-secondary);
}

.contact-content {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.contact-intro {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.contact-links {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
}

.contact-link {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    background: var(--bg-primary);
    border-radius: 0.5rem;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.contact-link:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    background: var(--accent-light);
}

.contact-icon {
    font-size: 1.5rem;
}

.contact-text {
    color: var(--text-primary);
    font-weight: 500;
}

.contact-location {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    margin-top: 2rem;
    color: var(--text-secondary);
}

.location-icon {
    font-size: 1.25rem;
}

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

.footer {
    background: var(--bg-primary);
    padding: 2rem 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
}

.footer p {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

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

/* ===========================
   Animations
   =========================== */

.fade-in {
    animation: fadeIn 1s ease-in;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in-section {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

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

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

@media (max-width: 768px) {
    .container {
        padding: 0 1rem;
    }

    section {
        padding: 3rem 0;
    }

    .nav-menu {
        display: none;
    }

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

    .hero-title {
        font-size: 1.5rem;
    }

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

    .hero-stats {
        flex-direction: column;
        gap: 1.5rem;
    }

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

    .btn {
        width: 100%;
    }

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

    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    h3 { font-size: 1.25rem; }

    .skills-grid,
    .projects-grid,
    .philosophy-grid,
    .education-grid {
        grid-template-columns: 1fr;
    }

    .timeline::before {
        left: 10px;
    }

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

    .timeline-marker {
        left: 2px;
    }

    .timeline-header {
        flex-direction: column;
    }

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

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

    .stat-number {
        font-size: 2rem;
    }

    .nav-container {
        padding: 1rem;
    }

    .theme-toggle {
        margin-left: auto;
    }
}

/* ===========================
   Utility Classes
   =========================== */

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

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }