@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+KR:wght@400;500;700&family=Roboto:wght@400;500;700&display=swap');

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

:root {
    --navy: #1a3a5c;
    --navy-dark: #0e2440;
    --cyan: #00b4d8;
    --cyan-dark: #0096b7;
    --text: #1e293b;
    --subtext: #64748b;
    --light: #f8fafc;
    --border: #e2e8f0;
}

html {
    scrollbar-gutter: stable;
}

body {
    font-family: "Roboto", "Noto Sans KR", sans-serif;
    color: var(--text);
    background: #ffffff;
    line-height: 1.7;
}

/* ── Navigation ── */
nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--navy);
    padding: 0 3rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    height: 56px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

nav .logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: #ffffff;
    font-weight: 700;
    font-size: 1.1rem;
    letter-spacing: 0.08rem;
    margin-right: auto;
    text-decoration: none;
}

nav .logo img {
    display: block;
    height: 36px;
    width: auto;
}

nav .logo:hover {
    color: #ffffff;
    background: transparent;
    opacity: 0.85;
}

nav a {
    color: #cbd5e1;
    text-decoration: none;
    font-size: 0.9rem;
    padding: 0.35rem 0.8rem;
    border-radius: 4px;
    transition: color 0.15s, background 0.15s;
}

nav a:hover {
    color: var(--cyan);
    background: rgba(255,255,255,0.07);
}

nav a.active {
    color: var(--cyan);
    border-bottom: 2px solid var(--cyan);
}

/* ── Hero ── */
.hero {
    background: linear-gradient(135deg, var(--navy) 0%, var(--navy-dark) 100%);
    color: white;
    padding: 6rem 3rem;
    text-align: center;
}

.hero h1 {
    font-size: 2.8rem;
    font-weight: 700;
    letter-spacing: 0.06rem;
}

.hero .fullname {
    color: var(--cyan);
    font-size: 1.15rem;
    margin-top: 0.6rem;
    font-weight: 500;
}

.hero .fullname-ko {
    color: #94a3b8;
    font-size: 1rem;
    margin-top: 0.2rem;
}

.hero .affil {
    color: #94a3b8;
    font-size: 0.95rem;
    margin-top: 1rem;
}

.hero .desc {
    color: #cbd5e1;
    margin-top: 1.5rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
    font-size: 1rem;
}

.hero .btn {
    display: inline-block;
    margin-top: 2.2rem;
    padding: 0.75rem 2.2rem;
    background: var(--cyan);
    color: white;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 700;
    font-size: 1rem;
    letter-spacing: 0.03rem;
    transition: background 0.15s, transform 0.1s;
}

.hero .btn:hover {
    background: var(--cyan-dark);
    transform: translateY(-1px);
}

/* ── Sections ── */
.content {
    max-width: 1100px;
    margin: auto;
    padding: 0 3rem;
}

section {
    padding: 4rem 0;
    border-bottom: 1px solid var(--border);
}

section:last-child {
    border-bottom: none;
}

.section-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--navy);
    border-bottom: 3px solid var(--cyan);
    display: inline-block;
    padding-bottom: 0.3rem;
    margin-bottom: 0.4rem;
}

.section-title-ko {
    font-size: 0.93rem;
    color: var(--subtext);
    margin-bottom: 1.8rem;
}

/* ── About ── */
.about-inner {
    max-width: 800px;
    width: 100%;
    margin: 0 auto;
    text-align: center;
}

.about-text {
    color: var(--text);
    font-size: 1rem;
    margin: 0 0 0.8rem;
    text-align: left;
}

.about-text-ko {
    color: var(--subtext);
    font-size: 0.97rem;
    text-align: left;
}

/* ── Research Cards ── */
.cards {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.2rem;
    margin-top: 0.5rem;
}

.card {
    border: 1px solid var(--border);
    border-top: 3px solid var(--cyan);
    border-radius: 8px;
    padding: 1.4rem;
    transition: box-shadow 0.15s, transform 0.15s;
}

.card:hover {
    box-shadow: 0 4px 16px rgba(0, 180, 216, 0.12);
    transform: translateY(-2px);
}

.card h3 {
    font-size: 1rem;
    font-weight: 700;
    color: var(--navy);
    margin-bottom: 0.3rem;
}

.card .card-ko {
    font-size: 0.88rem;
    color: var(--cyan-dark);
    margin-bottom: 0.6rem;
}

.card p {
    font-size: 0.92rem;
    color: var(--subtext);
}

/* ── Members ── */
.member-card {
    display: flex;
    align-items: center;
    gap: 2rem;
    background: var(--light);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 1.8rem 2rem;
    max-width: 600px;
    margin: 0 auto;
}

.member-avatar {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: var(--navy);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    font-weight: 700;
    flex-shrink: 0;
}

.member-info h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--navy);
}

.member-info .role {
    font-size: 0.92rem;
    color: var(--cyan-dark);
    font-weight: 500;
    margin-top: 0.15rem;
}

.member-info .affil {
    font-size: 0.9rem;
    color: var(--subtext);
    margin-top: 0.2rem;
}

.member-info a {
    font-size: 0.9rem;
    color: var(--cyan-dark);
    text-decoration: none;
    margin-top: 0.4rem;
    display: block;
}

.member-info a:hover { text-decoration: underline; }

/* ── Join Us ── */
.joinus-box {
    background: linear-gradient(135deg, var(--navy) 0%, var(--navy-dark) 100%);
    color: white;
    border-radius: 12px;
    padding: 2.5rem;
    max-width: 800px;
    margin: 0 auto;
}

.joinus-box h3 {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--cyan);
    margin-bottom: 0.3rem;
}

.joinus-box .ko {
    font-size: 0.93rem;
    color: #94a3b8;
    margin-bottom: 1.4rem;
}

.joinus-box ul {
    list-style: none;
    padding: 0;
}

.joinus-box ul li {
    padding: 0.4rem 0;
    font-size: 0.95rem;
    color: #cbd5e1;
    display: flex;
    gap: 0.7rem;
}

.joinus-box ul li::before {
    content: "▸";
    color: var(--cyan);
    flex-shrink: 0;
}

.joinus-box + .joinus-box {
    margin-top: 1.5rem;
}

.joinus-hr {
    border: none;
    border-top: 1px solid rgba(255,255,255,0.12);
    margin: 1.2rem 0;
}

.joinus-box .ko-list li {
    color: #94a3b8;
    font-size: 0.88rem;
}

.joinus-box ul li a,
.joinus-box .joinus-text a,
.joinus-box .joinus-text-ko a {
    color: var(--cyan);
    text-decoration: none;
}

.joinus-box ul li a:hover,
.joinus-box .joinus-text a:hover,
.joinus-box .joinus-text-ko a:hover {
    text-decoration: underline;
}

.joinus-text {
    font-size: 0.97rem;
    color: #cbd5e1;
    line-height: 1.8;
    margin-bottom: 0.4rem;
}

.joinus-text-ko {
    font-size: 0.93rem;
    color: #94a3b8;
    line-height: 1.8;
}

/* ── Members Groups ── */
.members-group {
    margin-bottom: 2.5rem;
}

.members-group:last-child {
    margin-bottom: 0;
}

.members-group-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--subtext);
    text-transform: uppercase;
    letter-spacing: 0.08rem;
    margin-bottom: 1rem;
    padding-bottom: 0.3rem;
    border-bottom: 1px solid var(--border);
}

.members-empty {
    color: var(--subtext);
    font-size: 0.95rem;
}

.members-empty a {
    color: var(--cyan-dark);
    text-decoration: none;
}

.members-empty a:hover { text-decoration: underline; }

/* ── Publications ── */
.pub-category {
    margin-bottom: 2.5rem;
}

.pub-category:last-child {
    margin-bottom: 0;
}

.pub-category-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--subtext);
    text-transform: uppercase;
    letter-spacing: 0.08rem;
    margin-bottom: 1rem;
    padding-bottom: 0.3rem;
    border-bottom: 1px solid var(--border);
}

.pub-list {
    list-style: none;
    padding: 0;
}

.pub-list li {
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
    padding: 0.9rem 0;
    border-bottom: 1px solid var(--border);
}

.pub-list li:last-child { border-bottom: none; }

.pub-title {
    font-weight: 500;
    color: var(--text);
    font-size: 1rem;
}

.pub-authors {
    font-size: 0.92rem;
    color: var(--subtext);
}

.pub-venue {
    font-size: 0.9rem;
    color: var(--cyan-dark);
}

.pub-venue a {
    color: var(--cyan-dark);
    text-decoration: none;
}

.pub-venue a:hover { text-decoration: underline; }

/* ── Contact ── */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    max-width: 800px;
    margin: 0 auto;
}

.contact-block {
    background: var(--light);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 1.8rem;
}

.contact-label {
    font-size: 0.83rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08rem;
    color: var(--cyan-dark);
    margin-bottom: 0.5rem;
}

.contact-value {
    font-size: 0.97rem;
    color: var(--text);
    line-height: 1.8;
}

.contact-value a {
    color: var(--cyan-dark);
    text-decoration: none;
}

.contact-value a:hover { text-decoration: underline; }

.contact-label-mt {
    margin-top: 1.5rem;
}

.contact-value-ko {
    font-size: 0.93rem;
    color: var(--subtext);
    line-height: 1.8;
    margin-top: 0.8rem;
}

/* ── Footer ── */
footer {
    background: var(--navy-dark);
    color: #64748b;
    text-align: center;
    padding: 2rem;
    font-size: 0.9rem;
    line-height: 1.9;
}

footer a {
    color: #94a3b8;
    text-decoration: none;
}

footer a:hover { color: var(--cyan); }

footer .footer-logo {
    display: block;
    width: 280px;
    height: auto;
    margin: 0 auto 0.5rem;
}

footer .footer-email {
    margin-top: 0.5rem;
}

footer .footer-copy {
    margin-top: 1rem;
    font-size: 0.83rem;
}

/* section-title on h2 resets browser default margin */
h2.section-title {
    margin: 0;
}

/* ── Responsive: Tablet (≤ 900px) ── */
@media (max-width: 900px) {
    .cards {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* ── Responsive: Mobile (≤ 640px) ── */
@media (max-width: 640px) {
    /* Nav */
    nav {
        height: auto;
        padding: 0.6rem 1rem;
        flex-wrap: wrap;
        row-gap: 0.3rem;
    }

    nav .logo {
        width: 100%;
        margin-right: 0;
    }

    nav .logo img {
        height: 30px;
    }

    nav a:not(.logo) {
        font-size: 0.82rem;
        padding: 0.25rem 0.5rem;
    }

    /* Hero */
    .hero {
        padding: 3.5rem 1.5rem;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero .desc,
    .hero .desc-ko {
        font-size: 0.88rem;
    }

    /* Content */
    .content {
        padding: 0 1.5rem;
    }

    /* Research cards */
    .cards {
        grid-template-columns: 1fr;
    }

    /* Member card */
    .member-card {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
        padding: 1.4rem;
    }

    /* Contact grid */
    .contact-grid {
        grid-template-columns: 1fr;
        gap: 1.2rem;
    }

    /* Join Us boxes */
    .joinus-box {
        padding: 1.8rem 1.4rem;
    }

    /* Footer */
    footer {
        padding: 1.5rem 1rem;
    }
}