:root {
    --primary: #000000;
    --secondary: #e5e7eb;
    --accent: #111827;
    --brand: #ba2636; /* Unified brand red */
    --text: #4b5563;
    --light: #f9fafb;
    --white: #ffffff;
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

html {
    scroll-behavior: smooth;
}

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

h1, h2, h3, h4, h5, h6 {
    letter-spacing: -0.02em;
    font-weight: 700;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    line-height: 1.7;
    color: var(--text);
    background-color: var(--white);
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Navigation */
.navbar {
    background: var(--white);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    text-decoration: none;
    display: flex;
    align-items: center;
}

.logo img {
    height: 40px;
    width: auto;
    display: block;
}

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

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li a {
    color: var(--text);
    text-decoration: none;
    margin-left: 2rem;
    font-size: 0.9rem;
    transition: color 0.3s;
}

.nav-links li a:hover { color: var(--brand); }

.nav-links li a.active {
    color: var(--brand);
    font-weight: 600;
}

/* Hero Section */
.hero {
    background: var(--white);
    color: var(--text);
    padding: 120px 0;
    text-align: center;
    background: linear-gradient(to bottom, #ffffff, var(--light));
}

.hero h1 {
    font-family: inherit;
    font-size: 3rem;
    margin-bottom: 1.5rem;
    line-height: 1.2;
    color: var(--accent);
}

.hero h1 .university-name {
    font-size: 0.6em;
    font-weight: 500;
    display: block;
}

.hero p {
    font-size: 1.2rem;
    max-width: 700px;
    margin: 0 auto 2rem;
}

.btn {
    display: inline-block;
    background: var(--accent);
    color: var(--white);
    padding: 0.8rem 2rem;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 500;
    transition: all 0.2s ease;
    box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
}

.btn:hover {
    background: var(--brand);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

/* Sections */
.section { padding: 80px 0; }
.bg-light { background: var(--light); }
.section-title {
    font-family: inherit;
    font-size: 2.2rem;
    margin-bottom: 4rem;
    text-align: center;
}

.section-subtitle {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    border-left: 4px solid var(--accent);
    counter-reset: pub-counter;
    padding-left: 1rem;
}

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

.grid-vertical {
    grid-template-columns: 1fr;
    max-width: 800px;
    margin: 0 auto;
}

.card {
    background: var(--white);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: none;
    border: 1px solid var(--secondary);
    margin-bottom: 2rem;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.card:hover {
    border-color: #d1d5db;
    box-shadow: var(--shadow-md);
}

.card h3 { margin-bottom: 1rem; color: var(--accent); }

/* Collapsible Cards */
.card.collapsible {
    padding: 0;
}

.card.collapsible summary {
    padding: 1.5rem 2rem;
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 700;
    color: var(--accent);
    font-size: 1.25rem;
    outline: none;
    user-select: none;
}

.card.collapsible summary::-webkit-details-marker { display: none; }
.card.collapsible summary::after { content: '+'; font-size: 1.5rem; transition: transform 0.3s; line-height: 1; }
.card.collapsible[open] summary::after { transform: rotate(45deg); }

.collapsible-content { 
    padding: 0 2rem 1.5rem; 
    counter-reset: pub-counter;
}

/* News List */
.news-list { list-style: none; }
.news-list li {
    display: flex;
    margin-bottom: 0.5rem;
    padding-bottom: 0.5rem;
}

.date {
    min-width: 150px;
    font-weight: 600;
    color: var(--accent);
}

/* Footer */
.footer { 
    color: var(--text); 
    padding: 80px 0 30px; 
    background: var(--light);
    border-top: 1px solid var(--secondary);
}
.footer-content { 
    display: grid; 
    grid-template-columns: 1fr 1fr; 
    gap: 4rem; 
    margin-bottom: 60px; 
}
.footer-column h4, .footer-column h5 { 
    color: var(--accent); 
    margin-bottom: 1.5rem; 
    font-size: 1.1rem;
}
.footer-column p { 
    font-size: 0.9rem; 
    line-height: 1.6;
    margin-bottom: 0.8rem;
    display: block;
    color: var(--text);
}
.footer-column a {
    font-size: 0.9rem;
    line-height: 1.6;
    margin-bottom: 0.8rem;
    display: block;
    text-decoration: none;
    color: var(--brand);
    font-weight: 500;
}
.footer-column:last-child {
    text-align: right;
}
.footer-column a:hover { color: var(--brand); text-decoration: underline; }
.footer-nav { list-style: none; }
.footer-nav li { margin-bottom: 0.5rem; }

.copyright { 
    text-align: center; 
    border-top: 1px solid var(--secondary); 
    padding-top: 30px; 
    font-size: 0.85rem; 
    color: #718096; 
}

/* Publications Section */
.publication-list {
    list-style: none;
    padding-left: 0;
    margin-bottom: 2rem;
}

.publication-list.bullet-list .publication-item {
    counter-increment: none;
}

.publication-list.bullet-list .publication-item::before {
    content: "•";
}

.year-header {
    font-size: 1.2rem;
    font-weight: 700;
    margin: 2rem 0 1rem 0;
    color: var(--text);
    border-bottom: 2px solid var(--secondary);
    padding-bottom: 0.2rem;
    display: block;
}

/* Collapsible Years in People Page */
.collapsible-year {
    margin-bottom: 1rem;
}

.collapsible-year summary.year-header {
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    outline: none;
    user-select: none;
}

.collapsible-year summary::-webkit-details-marker { display: none; }
.collapsible-year summary::after { content: '+'; font-size: 1.2rem; transition: transform 0.3s; }
.collapsible-year[open] summary::after { transform: rotate(45deg); }

.year-content {
    padding: 0.5rem 0 1.5rem 1rem;
}

.publication-item {
    counter-increment: pub-counter;
    margin-bottom: 0.7rem;
    padding-left: 2rem;
    position: relative;
    border: none;
}

.publication-item::before {
    content: counter(pub-counter) ".";
    position: absolute;
    left: 0;
    font-weight: 600;
}

.publication-item h3 {
    margin-top: 0;
    color: var(--text);
    font-size: 1.0rem;
    margin-bottom: 0.5rem;
}

.publication-item .authors, .publication-item .journal {
    font-size: 1.0rem;
    color: #64748b;
    margin-bottom: 0rem;
}

.publication-item .journal {
    font-style: normal; /* Removed italic for simplicity */
    color: var(--text);
    margin-bottom: 0.3rem;
}

.read-more {
    color: var(--brand);
    text-decoration: none;
    font-weight: 400;
    transition: opacity 0.3s;
}

.read-more:hover {
    text-decoration: underline;
    opacity: 0.8;
}

/* Language Switching */
body[data-lang="en"] .lang-jp { display: none; }
body[data-lang="jp"] .lang-en { display: none; }

.lang-switch-btn {
    background: none;
    border: 1px solid var(--brand);
    color: var(--brand);
    padding: 0.2rem 0.6rem;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.8rem;
    margin-left: 1.5rem;
    font-weight: 600;
}

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

@media (max-width: 768px) {
    .hero h1 {
        font-size: 2rem;
    }

    .navbar .container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
    }

    .nav-links li a {
        margin: 0.5rem 0.8rem;
    }

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

.contact-form .form-group {
    margin-bottom: 1.5rem;
}

.contact-form label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.contact-form input,
.contact-form textarea {
    width: 100%;
    padding: 0.8rem;
    border: 1px solid var(--secondary);
    border-radius: 4px;
    font-family: inherit;
}

.contact-form textarea {
    height: 150px;
    resize: vertical;
}

.info-item {
    margin-bottom: 2rem;
}

.access-info {
    margin-top: 4rem;
}