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

:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --accent-color: #3b82f6;
    --text-primary: #1e293b;
    --text-secondary: #475569;
    --text-light: #64748b;
    --background: #ffffff;
    --background-alt: #f8fafc;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
}

html {
    scroll-behavior: smooth;
}

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

/* ===== Navigation ===== */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
    transition: all 0.3s ease;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

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

.nav-menu a {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

.nav-menu a:hover {
    color: var(--primary-color);
}

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

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

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 4px;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    transition: all 0.3s ease;
}

/* ===== Hero Section ===== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 6rem 2rem;
    margin-top: 70px;
    overflow: hidden;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    opacity: 0.05;
    z-index: -1;
}

.hero-content {
    max-width: 800px;
    text-align: center;
    animation: fadeInUp 1s ease;
}

.hero-title {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

.hero-description {
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    border-radius: 0.5rem;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

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

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

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

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

/* ===== Sections ===== */
.section {
    padding: 5rem 2rem;
}

.section:nth-child(even) {
    background: var(--background-alt);
}

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

.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.section-line {
    width: 60px;
    height: 4px;
    background: linear-gradient(to right, var(--primary-color), var(--accent-color));
    margin: 0 auto;
    border-radius: 2px;
}

/* ===== About Section ===== */
.about-content {
    max-width: 900px;
    margin: 0 auto;
}

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

/* ===== Timeline (Experience) ===== */
.timeline {
    position: relative;
    max-width: 900px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 20px;
    top: 0;
    height: 100%;
    width: 2px;
    background: var(--border-color);
}

.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(--primary-color);
    border: 3px solid white;
    box-shadow: var(--shadow-md);
}

.timeline-content {
    background: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
}

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

.timeline-content h3 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.timeline-content h4 {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    font-weight: 600;
}

.location {
    color: var(--text-light);
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

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

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

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

/* ===== Education Grid ===== */
.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.education-card {
    background: white;
    padding: 2.5rem;
    border-radius: 1rem;
    text-align: center;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
}

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

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

.education-card h3 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.education-card h4 {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    font-weight: 600;
}

.institution {
    color: var(--text-light);
    font-size: 1rem;
}

/* ===== Skills Grid ===== */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.skill-card {
    background: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
}

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

.skill-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.skill-card h3 {
    font-size: 1.25rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-weight: 600;
}

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

/* ===== Patents Grid ===== */
.patents-grid {
    display: grid;
    gap: 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.patent-card {
    background: white;
    padding: 2.5rem;
    border-radius: 1rem;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
}

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

.patent-number {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

.patent-card h3 {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.patent-description {
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 1rem;
}

.co-inventors {
    color: var(--text-light);
    font-size: 0.875rem;
}

/* ===== Contact Section ===== */
.contact-content {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

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

.contact-info {
    display: grid;
    gap: 1.5rem;
}

.contact-item {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    font-size: 1.125rem;
}

.contact-label {
    font-weight: 600;
    color: var(--text-primary);
}

.contact-item a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

.contact-item a:hover {
    color: var(--secondary-color);
    text-decoration: underline;
}

/* ===== Footer ===== */
.footer {
    background: var(--text-primary);
    color: white;
    text-align: center;
    padding: 2rem;
}

.footer p {
    margin: 0;
}

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

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background: white;
        width: 100%;
        text-align: center;
        transition: left 0.3s ease;
        box-shadow: var(--shadow-lg);
        padding: 2rem 0;
    }

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

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

    .hero-subtitle {
        font-size: 1.25rem;
    }

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

    .section-header h2 {
        font-size: 2rem;
    }

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

    .timeline-item {
        padding-left: 50px;
    }

    .timeline-marker {
        left: 1px;
    }

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

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

    .btn {
        width: 100%;
        max-width: 300px;
    }

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

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

    .nav-container {
        padding: 1rem;
    }

    .section {
        padding: 3rem 1rem;
    }

    .timeline-content,
    .patent-card,
    .education-card {
        padding: 1.5rem;
    }
}