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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 60px 0 40px;
    text-align: center;
}

header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    font-weight: 600;
}

.subtitle {
    font-size: 1.2em;
    opacity: 0.95;
}

/* Navigation */
nav {
    background-color: white;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

nav .container {
    display: flex;
    gap: 30px;
    padding: 15px 20px;
}

nav a {
    color: #667eea;
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

nav a:hover {
    color: #764ba2;
}

nav a.active {
    color: #764ba2;
    font-weight: 600;
}

/* Main Content */
main {
    padding: 40px 20px;
}

section {
    background-color: white;
    margin-bottom: 40px;
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

section h2 {
    color: #667eea;
    margin-bottom: 30px;
    font-size: 2em;
    border-bottom: 3px solid #667eea;
    padding-bottom: 10px;
}

/* About Section */
.about-header {
    display: flex;
    gap: 30px;
    align-items: flex-start;
    margin-bottom: 30px;
}

.profile-image {
    flex-shrink: 0;
}

.profile-image img {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    object-fit: cover;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    background-color: #f0f0f0;
}

.about-text {
    flex: 1;
}

.about-text h2 {
    margin-top: 0;
}

#about p {
    font-size: 1.1em;
    color: #555;
    margin-bottom: 20px;
}

@media (max-width: 768px) {
    .about-header {
        flex-direction: column;
        align-items: center;
        text-align: center;
    }
    
    .profile-image img {
        width: 150px;
        height: 150px;
    }
}

/* Research Papers */
.year-heading {
    color: #667eea;
    font-size: 1.5em;
    margin-top: 40px;
    margin-bottom: 20px;
    border-bottom: 2px solid #667eea;
    padding-bottom: 8px;
}

.year-heading:first-of-type {
    margin-top: 0;
}

.papers-list {
    display: flex;
    flex-direction: column;
    gap: 30px;
    margin-bottom: 40px;
}

.paper {
    border-left: 4px solid #667eea;
    padding-left: 20px;
}

.paper-title {
    font-size: 1.4em;
    color: #333;
    margin-bottom: 10px;
}

.paper-authors {
    color: #666;
    font-style: italic;
    margin-bottom: 5px;
}

.paper-venue {
    color: #888;
    font-size: 0.95em;
    margin-bottom: 10px;
}

.paper-description {
    color: #555;
    margin-bottom: 15px;
    line-height: 1.6;
}

.paper-links {
    display: flex;
    gap: 10px;
}

/* Projects */
.projects-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
}

.project {
    border: 1px solid #e0e0e0;
    padding: 25px;
    border-radius: 8px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.project:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.project-title {
    font-size: 1.3em;
    color: #667eea;
    margin-bottom: 15px;
}

.project-description {
    color: #555;
    margin-bottom: 15px;
    line-height: 1.6;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
}

.tag {
    background-color: #e8eaf6;
    color: #667eea;
    padding: 5px 12px;
    border-radius: 20px;
    font-size: 0.85em;
    font-weight: 500;
}

.project-links {
    display: flex;
    gap: 10px;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 8px 16px;
    background-color: #667eea;
    color: white;
    text-decoration: none;
    border-radius: 5px;
    font-size: 0.9em;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

.btn:hover {
    background-color: #764ba2;
    transform: translateY(-2px);
}

/* Footer */
footer {
    background-color: #2c3e50;
    color: white;
    padding: 30px 0;
    margin-top: 60px;
}

footer .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

footer p {
    margin: 0;
}

.footer-links {
    display: flex;
    gap: 20px;
}

.footer-links a {
    color: white;
    text-decoration: none;
    transition: opacity 0.3s ease;
}

.footer-links a:hover {
    opacity: 0.8;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 2em;
    }

    .subtitle {
        font-size: 1em;
    }

    nav .container {
        flex-direction: column;
        gap: 10px;
    }

    section {
        padding: 25px;
    }

    section h2 {
        font-size: 1.5em;
    }

    .projects-list {
        grid-template-columns: 1fr;
    }

    footer .container {
        flex-direction: column;
        text-align: center;
    }
}

@media (max-width: 480px) {
    header {
        padding: 40px 0 30px;
    }

    header h1 {
        font-size: 1.6em;
    }

    section {
        padding: 20px;
    }

    .paper-title {
        font-size: 1.2em;
    }

    .project-title {
        font-size: 1.1em;
    }
}