/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans JP', 'Inter', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fafafa;
}

/* Navigation */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    border-bottom: 1px solid #e0e0e0;
    transition: all 0.3s ease;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo h2 {
    color: #2563eb;
    font-weight: 600;
    font-size: 1.5rem;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 30px;
}

.nav-link {
    text-decoration: none;
    color: #666;
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: #2563eb;
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 100%;
    height: 2px;
    background: #2563eb;
}

.lang-toggle {
    background: #2563eb;
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s ease;
}

.lang-toggle:hover {
    background: #1d4ed8;
    transform: translateY(-1px);
}

/* Main content */
.main-content {
    margin-top: 70px;
    min-height: calc(100vh - 70px);
}

.page {
    display: none;
    animation: fadeIn 0.5s ease-in-out;
}

.page.active {
    display: block;
}

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

/* Hero section */
.hero-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 80px 20px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.3);
    z-index: 1;
}

.hero-image {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
}

.hero-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
    margin: 0 auto;
}

.hero-content h1 {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.hero-content h2 {
    font-size: 1.5rem;
    font-weight: 400;
    margin-bottom: 30px;
    opacity: 0.9;
}

.hero-content p {
    font-size: 1.1rem;
    line-height: 1.8;
    opacity: 0.9;
}

/* Content sections */
.content-section {
    max-width: 1200px;
    margin: 0 auto;
    padding: 60px 20px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
}

.content-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 60px 20px;
}

.research-areas,
.purpose {
    background: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.research-areas:hover,
.purpose:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.15);
}

.research-areas h3,
.purpose h3 {
    color: #2563eb;
    font-size: 1.3rem;
    margin-bottom: 20px;
    font-weight: 600;
}

.research-areas ul,
.purpose ul {
    list-style: none;
}

.research-areas li,
.purpose li {
    padding: 10px 0;
    border-bottom: 1px solid #f0f0f0;
    position: relative;
    padding-left: 20px;
}

.research-areas li:before,
.purpose li:before {
    content: '▶';
    color: #2563eb;
    position: absolute;
    left: 0;
}

.research-areas li:last-child,
.purpose li:last-child {
    border-bottom: none;
}

/* Diagram section */
.diagram-section {
    margin-top: 60px;
    text-align: center;
}

.diagram-section h3 {
    color: #2563eb;
    font-size: 1.5rem;
    margin-bottom: 30px;
    font-weight: 600;
}

.diagram-image {
    max-width: 100%;
    height: auto;
    border-radius: 12px;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}

.diagram-image:hover {
    transform: scale(1.02);
}

/* Publications */
.publication {
    background: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    margin-bottom: 40px;
}

.publication h2 {
    color: #2563eb;
    font-size: 1.8rem;
    margin-bottom: 30px;
    font-weight: 600;
}

.publication-details,
.abstract,
.keywords,
.citation,
.bibtex,
.pdf-embed {
    margin-bottom: 30px;
}

.publication-details p,
.abstract p,
.keywords p,
.citation p {
    margin-bottom: 10px;
}

.abstract h3,
.keywords h3,
.citation h3,
.bibtex h3,
.pdf-embed h3 {
    color: #374151;
    font-size: 1.2rem;
    margin-bottom: 15px;
    font-weight: 600;
}

.bibtex pre {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    overflow-x: auto;
    border-left: 4px solid #2563eb;
}

.bibtex code {
    font-family: 'Courier New', monospace;
    font-size: 0.9rem;
    color: #374151;
}

/* Contact */
.contact-info {
    background: white;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    margin: 30px 0;
}

.contact-info p {
    margin-bottom: 15px;
    font-size: 1.1rem;
}

.privacy-note {
    background: #fef3c7;
    padding: 20px;
    border-radius: 8px;
    border-left: 4px solid #f59e0b;
    margin: 30px 0;
}

.contact-form {
    background: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    margin-top: 40px;
}

.contact-form h3 {
    color: #2563eb;
    font-size: 1.3rem;
    margin-bottom: 20px;
    font-weight: 600;
}

/* Footer */
.footer {
    background: #1f2937;
    color: white;
    text-align: center;
    padding: 40px 20px;
    margin-top: 80px;
}

.footer-content p {
    opacity: 0.8;
}

/* Responsive design */
@media (max-width: 768px) {
    .nav-menu {
        gap: 15px;
    }
    
    .nav-link {
        font-size: 0.9rem;
    }
    
    .hero-content h1 {
        font-size: 2.5rem;
    }
    
    .hero-content h2 {
        font-size: 1.2rem;
    }
    
    .content-section {
        grid-template-columns: 1fr;
        gap: 30px;
        padding: 40px 20px;
    }
    
    .content-container {
        padding: 40px 20px;
    }
    
    .research-areas,
    .purpose,
    .publication,
    .contact-form {
        padding: 30px 20px;
    }
}

@media (max-width: 480px) {
    .nav-container {
        padding: 0 15px;
    }
    
    .nav-menu {
        gap: 10px;
    }
    
    .nav-link {
        font-size: 0.8rem;
    }
    
    .lang-toggle {
        padding: 6px 12px;
        font-size: 0.8rem;
    }
    
    .hero-content h1 {
        font-size: 2rem;
    }
    
    .hero-content h2 {
        font-size: 1rem;
    }
    
    .hero-content p {
        font-size: 1rem;
    }
}