/* ===== Base Variables & Setup ===== */
:root {
    --primary: #5ba4e6;
    /* Sky Blue Pastel Primary */
    --primary-dark: #468acb;
    --secondary: #1a365d;
    /* Soft Navy */
    --accent: #93c5fd;
    /* Light Pastel Blue */
    --text-main: #334155;
    --text-muted: #64748b;
    --bg-light: #f0f7ff;
    /* Very faint Sky Blue */
    --bg-white: #ffffff;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
    font-family: 'Inter', sans-serif;
}

body {
    color: var(--text-main);
    line-height: 1.6;
    background-color: var(--bg-white);
    overflow-x: hidden;
}

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

ul {
    list-style: none;
}

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

.mt-3 {
    margin-top: 1.5rem;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.highlight {
    color: var(--primary);
}

.highlight-link {
    color: var(--primary);
    font-weight: 600;
}

.highlight-link:hover {
    text-decoration: underline;
}

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

.bg-primary {
    background-color: var(--primary);
    color: #fff;
}

/* ===== Typography ===== */
h1,
h2,
h3,
h4 {
    color: var(--secondary);
    font-weight: 700;
    line-height: 1.2;
}

.section {
    padding: 4rem 0;
}

.section-header {
    text-align: center;
    margin-bottom: 2rem;
}

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.divider {
    height: 4px;
    width: 60px;
    background: var(--primary);
    margin: 0 auto;
    border-radius: 2px;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 0.8rem 2rem;
    border-radius: 50px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

.btn-secondary {
    background: transparent;
    color: #fff;
    border-color: rgba(255, 255, 255, 0.8);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: #fff;
    transform: translateY(-2px);
}

/* ===== Navbar ===== */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    transition: var(--transition);
    padding: 1rem 0;
    background: rgba(255, 255, 255, 0.97);
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
    border-bottom: 1px solid #eee;
}

.navbar.scrolled {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem 0;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
}

.navbar-subpage {
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.95) !important;
    padding: 1rem 5% !important;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.05) !important;
    border-bottom: 1px solid #eee;
    z-index: 1000;
}

.navbar-subpage .logo {
    color: var(--secondary) !important;
}

.navbar-subpage .nav-links a {
    color: var(--secondary) !important;
}

.navbar-subpage .nav-links a.active {
    color: var(--primary) !important;
    font-weight: 700;
}

.navbar-subpage .hamburger {
    color: var(--secondary) !important;
}

.navbar.scrolled .logo,
.navbar.scrolled .nav-links a {
    color: var(--secondary);
}

.navbar.scrolled .btn-contact {
    background: var(--primary);
    color: #fff;
}

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

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: #fff;
    letter-spacing: -0.5px;
}

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

.nav-links {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.nav-links a {
    color: var(--secondary);
    font-weight: 500;
    font-size: 0.85rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    line-height: 1.2;
    text-align: center;
}

.nav-links a .nav-ko {
    font-size: 0.7rem;
    font-weight: 300;
    color: var(--text-muted);
    margin-top: 1px;
}

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

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

.btn-contact {
    background: rgba(255, 255, 255, 0.1);
    padding: 0.6rem 1.5rem;
    border-radius: 50px;
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.btn-contact:hover {
    background: var(--primary) !important;
    border-color: var(--primary);
    color: #fff !important;
}

.hamburger {
    display: none;
    color: #fff;
    font-size: 1.5rem;
    cursor: pointer;
}

.navbar.scrolled .hamburger {
    color: var(--secondary);
}

/* ===== Hero Section ===== */
.hero {
    min-height: unset;
    height: auto;
    padding: 5rem 1rem 2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    background: linear-gradient(135deg, rgba(160, 200, 240, 0.85) 0%, rgba(220, 240, 255, 0.9) 100%),
        url('https://images.unsplash.com/photo-1518770660439-4636190af475?ixlib=rb-4.0.3&auto=format&fit=crop&w=2070&q=80') center/cover;
    color: var(--secondary);
    text-align: center;
}

.hero-content {
    max-width: 800px;
    z-index: 2;
    padding-top: 0;
}

.hero-title {
    font-size: 2.8rem;
    margin-bottom: 0.8rem;
    color: #fff;
    animation: slideUp 1s ease-out;
}

.hero-subtitle {
    font-size: 1.5rem;
    font-weight: 300;
    margin-bottom: 1rem;
    opacity: 0.9;
    animation: slideUp 1s ease-out 0.2s backwards;
}

.hero-text {
    font-size: 1.1rem;
    margin-bottom: 2.5rem;
    color: rgba(255, 255, 255, 0.8);
    animation: slideUp 1s ease-out 0.4s backwards;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    animation: slideUp 1s ease-out 0.6s backwards;
}

.scroll-down {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    animation: bounce 2s infinite;
}

.scroll-down a {
    color: rgba(255, 255, 255, 0.7);
    font-size: 2rem;
}

.about-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
    align-items: center;
}

.about-text p {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
}

.about-image {
    max-width: 280px;
    margin: 0 auto;
}

.about-image img {
    width: 100%;
    height: auto;
    border-radius: 16px;
}

.about-features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}

.feature-card {
    background: #fff;
    padding: 2rem;
    border-radius: 16px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
    text-align: center;
    transition: var(--transition);
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.08);
}

.feature-card i {
    color: var(--primary);
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

.feature-card p {
    font-size: 0.9rem;
    color: var(--text-muted);
}

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

.research-card {
    background: #fff;
    border: 1px solid rgba(0, 0, 0, 0.05);
    padding: 2.5rem;
    border-radius: 16px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.research-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: var(--primary);
    transform: scaleX(0);
    transform-origin: left;
    transition: var(--transition);
}

.research-card:hover {
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.06);
    transform: translateY(-5px);
}

.research-card:hover::before {
    transform: scaleX(1);
}

.card-icon {
    width: 60px;
    height: 60px;
    background: var(--bg-light);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: var(--primary);
    margin-bottom: 1.5rem;
}

.research-card h3 {
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.research-card p {
    color: var(--text-muted);
}

/* ===== Members Section ===== */
.subsection-title {
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
    color: var(--secondary);
    border-left: 4px solid var(--primary);
    padding-left: 1rem;
}

.pi-section {
    margin-bottom: 4rem;
}

.pi-card {
    max-width: 400px;
    background: #fff;
    border-radius: 12px;
    padding: 2rem;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.03);
    border-left: 4px solid var(--primary);
}

.members-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 1.5rem;
}

.member-card {
    background: #fff;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.03);
    transition: var(--transition);
}

.member-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.06);
}

.member-card h4 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

.member-role {
    color: var(--primary);
    font-weight: 600;
    font-size: 0.9rem;
}

.member-major {
    color: var(--text-main);
    font-size: 0.9rem;
    opacity: 0.9;
}

.member-research {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-top: 0.3rem;
    padding-top: 0.5rem;
    border-top: 1px dashed rgba(0, 0, 0, 0.1);
}

/* ===== Publications Section ===== */
.pub-list {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    max-width: 900px;
    margin: 0 auto;
}

.pub-item {
    display: flex;
    gap: 2rem;
    align-items: center;
    background: #fff;
    padding: 1.5rem 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.03);
    transition: var(--transition);
    border-left: 4px solid transparent;
}

.pub-item:hover {
    border-left-color: var(--primary);
    transform: translateX(10px);
    background: var(--bg-light);
}

.pub-year {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary);
    min-width: 60px;
}

.pub-info h4 {
    font-size: 1.1rem;
    margin-bottom: 0.3rem;
    color: var(--secondary);
}

.pub-journal {
    color: var(--text-muted);
    font-weight: 600;
    font-size: 0.95rem;
    font-style: italic;
}

/* ===== Recruit Banner ===== */
.recruit-banner {
    padding: 4rem 0;
}

.recruit-banner h2 {
    color: #fff;
    margin-bottom: 1rem;
    font-size: 2rem;
}

.recruit-banner p {
    font-size: 1.1rem;
    opacity: 0.9;
    margin-bottom: 2rem;
}

.recruit-benefits {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 1rem;
}

.recruit-benefits span {
    background: rgba(255, 255, 255, 0.1);
    padding: 0.5rem 1.5rem;
    border-radius: 50px;
    font-weight: 600;
    font-size: 1rem;
}

/* ===== News Section ===== */
.news-list {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.news-item {
    background: #fff;
    padding: 1.5rem 2rem;
    border-radius: 12px;
    display: flex;
    align-items: center;
    gap: 2rem;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.03);
    transition: var(--transition);
    border-left: 4px solid transparent;
}

.news-item:hover {
    transform: translateX(10px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.05);
    border-left-color: var(--primary);
}

.news-badge {
    padding: 0.4rem 1rem;
    border-radius: 50px;
    font-size: 0.8rem;
    font-weight: 600;
    color: #fff;
    background: var(--text-muted);
    min-width: 80px;
    text-align: center;
}

.news-content h4 {
    margin-bottom: 0.3rem;
    font-size: 1.1rem;
}

.news-content p {
    margin: 0;
    font-size: 0.95rem;
    color: var(--text-muted);
}

.bg-success {
    background: #10b981;
}

.bg-info {
    background: #0ea5e9;
}

.bg-warning {
    background: #f59e0b;
}

/* ===== Footer ===== */
.footer {
    background: var(--secondary);
    color: #fff;
    padding: 4rem 0 2rem;
}

/* ===== Global Bilingual Utilities ===== */
.bilingual-group {
    margin-bottom: 1rem;
}

.text-en {
    font-weight: 600;
    line-height: 1.4;
}

.text-ko {
    font-size: 0.95em;
    margin-top: 0.2rem;
    line-height: 1.4;
    font-weight: 400;
}

.section-header .text-en {
    margin-bottom: 0;
}

.section-header .text-ko {
    color: var(--text-muted);
    font-size: 1.1rem;
    margin-top: 0.3rem;
    margin-bottom: 1.5rem;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 2fr 1fr;
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-brand h2 {
    color: #fff;
    font-size: 2rem;
    margin-bottom: 1rem;
}

.footer-brand span {
    color: var(--primary);
}

.footer-brand p {
    color: rgba(255, 255, 255, 0.6);
    max-width: 300px;
}

.footer-contact h3,
.footer-links h3 {
    color: #fff;
    font-size: 1.2rem;
    margin-bottom: 1.5rem;
}

.footer-contact p {
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 1rem;
    display: flex;
    gap: 1rem;
    font-size: 0.95rem;
}

.footer-contact i {
    color: var(--primary);
    margin-top: 0.3rem;
}

.footer-links ul li {
    margin-bottom: 0.8rem;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.7);
}

.footer-links a:hover {
    color: var(--primary);
    padding-left: 5px;
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.5);
    font-size: 0.9rem;
}

/* ===== Animations & Utilities ===== */
@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {

    0%,
    20%,
    50%,
    80%,
    100% {
        transform: translateY(0) translateX(-50%);
    }

    40% {
        transform: translateY(-20px) translateX(-50%);
    }

    60% {
        transform: translateY(-10px) translateX(-50%);
    }
}

.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 992px) {
    .about-grid {
        grid-template-columns: 1fr;
    }

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

    .hero-title {
        font-size: 2.8rem;
    }

    .recruit-benefits {
        flex-direction: column;
        gap: 1rem;
    }
}

@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        background: var(--bg-white);
        top: 0;
        right: -100%;
        width: 250px;
        height: 100vh;
        flex-direction: column;
        justify-content: center;
        box-shadow: -5px 0 20px rgba(0, 0, 0, 0.1);
        transition: right 0.4s ease;
    }

    .nav-links.active {
        right: 0;
    }

    .nav-links a {
        color: var(--secondary);
        font-size: 1.2rem;
    }

    .nav-links .btn-contact {
        background: var(--primary);
        color: #fff;
        border-color: var(--primary);
    }

    .hamburger {
        display: block;
        z-index: 1001;
    }

    .hamburger.active {
        color: var(--secondary);
    }

    .hero-title {
        font-size: 2.2rem;
    }

    .news-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }

    .news-badge {
        align-self: flex-start;
    }

    .pub-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
}