@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

/* CSS Variables */
:root {
    --color-primary: #2c3e50;
    --color-secondary: #34495e;
    --color-accent: #3498db;
    --color-text: #2c3e50;
    --color-text-light: #7f8c8d;
    --color-bg: #ffffff;
    --color-bg-alt: #f8f9fa;
    --color-border: #e0e0e0;
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --max-width: 1200px;
    --nav-height: 60px;
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    color: var(--color-text);
    background-color: var(--color-bg);
    line-height: 1.7;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: 1rem;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
}

h2 {
    font-size: 2rem;
}

h3 {
    font-size: 1.5rem;
}

p {
    margin-bottom: 1rem;
}

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

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

/* Container */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 2rem;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--color-bg);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    z-index: 1000;
    height: var(--nav-height);
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 100%;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-primary);
}

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

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

.nav-link {
    color: var(--color-text);
    font-weight: 500;
    font-size: 0.95rem;
    position: relative;
}

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

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: var(--color-primary);
    transition: var(--transition);
    border-radius: 2px;
}

/* Hero Section */
.hero {
    margin-top: var(--nav-height);
    padding: 2.5rem 0;
    background: linear-gradient(135deg, #f8f9fa 0%, #ffffff 100%);
    border-bottom: 1px solid var(--color-border);
}

.hero-content {
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 3rem;
    align-items: start;
}

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

.hero-photo {
    margin-bottom: 1.5rem;
}

.hero-photo img {
    width: 216px;
    height: 216px;
    border-radius: 50%;
    object-fit: cover;
    border: 4px solid var(--color-bg);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.photo-placeholder {
    width: 216px;
    height: 216px;
    border-radius: 50%;
    background: var(--color-bg-alt);
    border: 3px dashed var(--color-border);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto;
    color: var(--color-text-light);
    font-weight: 500;
}

.hero-title {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    color: var(--color-primary);
}

.hero-subtitle {
    font-size: 1rem;
    color: var(--color-text-light);
    margin-bottom: 0.25rem;
    font-weight: 500;
}

.hero-social-links {
    display: flex;
    justify-content: center;
    gap: 0.75rem;
    margin-top: 1rem;
}

.hero-social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: var(--color-bg-alt);
    border-radius: 50%;
    color: var(--color-primary);
    transition: var(--transition);
}

.hero-social-link:hover {
    background: var(--color-accent);
    color: white;
    transform: translateY(-2px);
}

.hero-right {
    text-align: left;
}

/* Sections */
.section {
    padding: 3rem 0;
}

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

.section-title {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--color-primary);
    position: relative;
    padding-bottom: 0.75rem;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background: var(--color-accent);
}

/* About Section */
.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.about-content h3 {
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: var(--color-primary);
}

.about-content ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

.about-content li {
    margin-bottom: 0.75rem;
}

/* Publication Categories */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
}

.publication-category {
    background: var(--color-bg);
    padding: 1.5rem;
    border-radius: 10px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
    border-left: 4px solid var(--color-accent);
}

.category-title {
    color: var(--color-primary);
    font-size: 1.3rem;
    margin-bottom: 0.75rem;
    padding-bottom: 0.4rem;
    border-bottom: 2px solid var(--color-bg-alt);
}

.papers-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.paper-item {
    padding: 0.85rem;
    background: var(--color-bg-alt);
    border-radius: 6px;
    transition: var(--transition);
}

.paper-item:hover {
    background: #f0f2f5;
    transform: translateX(5px);
}

.paper-item h4 {
    color: var(--color-primary);
    font-size: 1rem;
    margin-bottom: 0.3rem;
    line-height: 1.3;
}

.paper-authors {
    color: var(--color-text-light);
    font-size: 0.85rem;
    margin-bottom: 0.15rem;
    font-style: italic;
    line-height: 1.3;
}

.paper-venue {
    color: var(--color-text);
    font-size: 0.85rem;
    margin-bottom: 0.5rem;
    line-height: 1.3;
}

.paper-links {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.paper-link {
    display: inline-block;
    padding: 0.4rem 1rem;
    background: var(--color-accent);
    color: white;
    border-radius: 4px;
    font-size: 0.85rem;
    font-weight: 500;
    transition: var(--transition);
}

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

/* Projects Section */
.projects-content {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

/* Blog Grid */
.blog-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.blog-card {
    background: var(--color-bg);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
}

.blog-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
}

.blog-card h3 {
    margin-bottom: 1rem;
}

.blog-card h3 a {
    color: var(--color-primary);
}

.blog-card h3 a:hover {
    color: var(--color-accent);
}

/* Button */
.btn {
    display: inline-block;
    padding: 0.75rem 2rem;
    background: var(--color-accent);
    color: white;
    border-radius: 5px;
    font-weight: 500;
    transition: var(--transition);
    margin-top: 1rem;
}

.btn:hover {
    background: var(--color-primary);
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(52, 152, 219, 0.3);
}

/* Contact Section */
.contact-content {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    margin-top: 2rem;
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 50px;
    height: 50px;
    background: var(--color-bg-alt);
    border-radius: 50%;
    color: var(--color-primary);
    transition: var(--transition);
}

.social-link:hover {
    background: var(--color-accent);
    color: white;
    transform: translateY(-3px);
    box-shadow: 0 4px 12px rgba(52, 152, 219, 0.3);
}

.social-link svg {
    width: 24px;
    height: 24px;
}

/* Footer */
.footer {
    background: var(--color-primary);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

.footer p {
    margin: 0;
    font-size: 0.9rem;
}

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

    .nav-menu {
        position: fixed;
        top: var(--nav-height);
        left: -100%;
        width: 100%;
        height: calc(100vh - var(--nav-height));
        background: var(--color-bg);
        flex-direction: column;
        align-items: center;
        padding-top: 2rem;
        gap: 1.5rem;
        transition: var(--transition);
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
    }

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

    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }

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

    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(7px, -6px);
    }

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

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

    .hero-right {
        text-align: left;
    }

    .hero-title {
        font-size: 1.75rem;
    }

    .hero-subtitle {
        font-size: 0.95rem;
    }

    .hero-photo img,
    .photo-placeholder {
        width: 180px;
        height: 180px;
    }

    h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.75rem;
    }

    .section {
        padding: 3rem 0;
    }

    .hero {
        padding: 3rem 0;
    }

    .container {
        padding: 0 1.5rem;
    }

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

    .publication-category {
        padding: 1.25rem;
    }

    .category-title {
        font-size: 1.15rem;
    }

    .paper-item {
        padding: 0.75rem;
    }

    .paper-item h4 {
        font-size: 0.95rem;
    }

    .paper-authors,
    .paper-venue {
        font-size: 0.8rem;
    }

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

@media (max-width: 480px) {
    .hero-title {
        font-size: 1.75rem;
    }

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

    .social-links {
        gap: 1rem;
    }

    .social-link {
        width: 45px;
        height: 45px;
    }
}