@import url('https://fonts.googleapis.com/css2?family=Spectral:ital,wght@0,300;0,400;0,600;1,400&family=DM+Sans:wght@300;400;500&family=Noto+Serif+KR:wght@400;600&display=swap');

:root {
  --bg: #f7f6f2;
  --surface: #ffffff;
  --text: #1c1c1c;
  --text-muted: #6b6b6b;
  --text-light: #9a9a9a;
  --accent: #1a3a5c;
  --accent-light: #e8eef4;
  --gold: #b8952a;
  --border: #e2e0d8;
  --nav-height: 64px;
  --max-width: 860px;
  --font-serif: 'Spectral', 'Noto Serif KR', Georgia, serif;
  --font-sans: 'DM Sans', system-ui, sans-serif;
}

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

html {
  font-size: clamp(14.5px, 14px + 0.25vw, 17px);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

/* ── Navigation ── */
nav {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  height: var(--nav-height);
  display: flex;
  align-items: center;
  padding: 0 clamp(1rem, 0.5rem + 1.5vw, 2rem);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-inner {
  max-width: var(--max-width);
  width: 100%;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.nav-brand {
  font-family: var(--font-serif);
  font-size: clamp(0.95rem, 0.9rem + 0.2vw, 1.05rem);
  font-weight: 600;
  color: var(--accent);
  text-decoration: none;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.nav-links {
  display: flex;
  gap: 0;
  list-style: none;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.nav-links a {
  display: block;
  padding: 0.4rem clamp(0.5rem, 0.3rem + 0.4vw, 0.85rem);
  font-size: clamp(0.78rem, 0.74rem + 0.15vw, 0.9rem);
  font-weight: 400;
  color: var(--text-muted);
  text-decoration: none;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
  background: var(--accent-light);
}

/* ── Page layout ── */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding:
    clamp(2rem, 1.5rem + 1.5vw, 3rem)
    clamp(1.1rem, 0.5rem + 1.5vw, 2rem)
    clamp(3rem, 4vw, 5rem);
}

/* ── Typography ── */
h1 {
  font-family: var(--font-serif);
  font-size: clamp(1.5rem, 1.2rem + 1.5vw, 2.15rem);
  font-weight: 600;
  line-height: 1.25;
  color: var(--accent);
  margin-bottom: 0.5rem;
  letter-spacing: -0.01em;
}

h2 {
  font-family: var(--font-serif);
  font-size: clamp(1.05rem, 0.95rem + 0.55vw, 1.3rem);
  font-weight: 600;
  color: var(--text);
  margin-bottom: 1rem;
  margin-top: clamp(2rem, 4vw, 2.75rem);
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border);
}

h3 {
  font-size: clamp(0.82rem, 0.78rem + 0.1vw, 0.92rem);
  font-weight: 500;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 1rem;
}

p {
  margin-bottom: 1rem;
  font-size: clamp(0.9rem, 0.85rem + 0.2vw, 0.98rem);
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Home hero ── */
.hero {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: clamp(1.25rem, 0.5rem + 2vw, 2rem);
  align-items: start;
  padding: clamp(1.75rem, 4vw, 2.5rem) 0 clamp(2rem, 4vw, 3rem);
  border-bottom: 1px solid var(--border);
  margin-bottom: clamp(1.75rem, 4vw, 2.5rem);
}

.hero-photo {
  width: clamp(86px, 14vw, 120px);
  height: clamp(86px, 14vw, 120px);
  border-radius: 4px;
  object-fit: cover;
  border: 1px solid var(--border);
}

.hero-name {
  font-family: var(--font-serif);
  font-size: clamp(1.4rem, 1.1rem + 1.4vw, 1.85rem);
  font-weight: 600;
  color: var(--accent);
  line-height: 1.2;
  margin-bottom: 0.25rem;
}

.hero-name-kr {
  font-family: 'Noto Serif KR', serif;
  font-size: clamp(0.9rem, 0.85rem + 0.2vw, 1.05rem);
  color: var(--text-muted);
  margin-bottom: 0.75rem;
  font-weight: 400;
}

.hero-position {
  font-size: clamp(0.84rem, 0.8rem + 0.2vw, 0.95rem);
  color: var(--text-muted);
  margin-bottom: 0.2rem;
}

.hero-links {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-top: 1rem;
}

.hero-links a {
  font-size: clamp(0.74rem, 0.72rem + 0.1vw, 0.82rem);
  padding: 0.3rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 20px;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 0.35rem;
  transition: border-color 0.15s, color 0.15s;
}

.hero-links a:hover {
  border-color: var(--accent);
  color: var(--accent);
  text-decoration: none;
}

/* ── News / updates ── */
.news-item {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 1rem;
  padding: 0.85rem 0;
  border-bottom: 1px solid var(--border);
  font-size: clamp(0.85rem, 0.82rem + 0.15vw, 0.95rem);
}

.news-date {
  color: var(--text-light);
  font-size: clamp(0.74rem, 0.72rem + 0.1vw, 0.82rem);
  padding-top: 0.1rem;
}

/* ── Publications ── */
.pub-filters {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.filter-btn {
  font-family: var(--font-sans);
  font-size: clamp(0.74rem, 0.72rem + 0.1vw, 0.82rem);
  padding: 0.35rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: 20px;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.15s;
}

.filter-btn:hover, .filter-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

.pub-section { margin-bottom: 2.5rem; }

.pub-section-title {
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--gold);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

.pub-item {
  padding: 0.75rem 0;
  border-bottom: 1px solid var(--border);
  font-size: clamp(0.85rem, 0.82rem + 0.15vw, 0.95rem);
  line-height: 1.65;
}

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

.pub-item em { font-style: italic; }

.pub-links {
  margin-top: 0.3rem;
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.pub-link {
  font-size: 0.75rem;
  padding: 0.15rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text-muted);
  transition: all 0.15s;
}

.pub-link:hover {
  border-color: var(--accent);
  color: var(--accent);
  text-decoration: none;
}

.pub-link.pdf { border-color: #c9a84c; color: #8a6f22; }

/* ── Research interests ── */
.research-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(0.75rem, 1.5vw, 1rem);
  margin-bottom: 2rem;
}

.research-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: clamp(1rem, 0.75rem + 1vw, 1.4rem);
  transition: border-color 0.15s, box-shadow 0.15s;
}

.research-card:hover {
  border-color: var(--accent);
  box-shadow: 0 1px 4px rgba(26, 58, 92, 0.08);
}

.research-card-title {
  font-size: clamp(0.82rem, 0.78rem + 0.2vw, 0.92rem);
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.research-card p {
  font-size: clamp(0.82rem, 0.78rem + 0.15vw, 0.9rem);
  color: var(--text-muted);
  margin-bottom: 0;
}

.research-card-latest {
  margin-top: 0.7rem;
  padding-top: 0.55rem;
  border-top: 1px dashed var(--border);
  font-size: clamp(0.76rem, 0.74rem + 0.1vw, 0.83rem);
  color: var(--text-light);
  line-height: 1.5;
}

.research-card-latest-label {
  display: inline-block;
  color: var(--gold);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.68rem;
  margin-right: 0.35rem;
}

.research-card-latest a { color: var(--accent); }

/* ── Teaching ── */
.course-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: clamp(1.1rem, 0.75rem + 1.2vw, 1.5rem);
  margin-bottom: 1rem;
}

.course-title {
  font-family: var(--font-serif);
  font-size: clamp(0.96rem, 0.9rem + 0.3vw, 1.1rem);
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 0.2rem;
}

.course-meta {
  font-size: clamp(0.74rem, 0.72rem + 0.1vw, 0.82rem);
  color: var(--text-light);
  margin-bottom: 0.75rem;
}

.course-desc {
  font-size: clamp(0.82rem, 0.78rem + 0.2vw, 0.9rem);
  color: var(--text-muted);
  margin-bottom: 0;
}

/* ── CV ── */
.cv-section { margin-bottom: 2rem; }

.cv-item {
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 1rem;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--border);
  font-size: clamp(0.85rem, 0.82rem + 0.15vw, 0.95rem);
}

.cv-year {
  color: var(--text-light);
  font-size: clamp(0.78rem, 0.76rem + 0.1vw, 0.88rem);
}

.cv-download {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--accent);
  color: white;
  padding: 0.6rem 1.25rem;
  border-radius: 6px;
  font-size: clamp(0.82rem, 0.78rem + 0.2vw, 0.9rem);
  margin-bottom: 2rem;
  transition: opacity 0.15s;
}

.cv-download:hover { opacity: 0.85; text-decoration: none; }

/* ── Footer ── */
footer {
  text-align: center;
  padding: 2rem clamp(1rem, 4vw, 2rem);
  font-size: clamp(0.74rem, 0.72rem + 0.1vw, 0.82rem);
  color: var(--text-light);
  border-top: 1px solid var(--border);
  margin-top: 3rem;
}

/* ── Responsive breakpoints ──
   Tablet (≤768px): tighter nav
   Mobile  (≤640px): hide redundant nav-brand; 5 links fill the bar evenly
   Small   (≤380px): tighter link padding/font + stacked news/cv items   */

@media (max-width: 768px) {
  :root { --nav-height: 58px; }
  h2 { margin-top: 2rem; }
}

@media (max-width: 640px) {
  /* Nav-brand ("Seungho Jung") is hidden — the page already shows the name,
     so removing it from the menu frees space for all 5 links to fit on phones. */
  :root { --nav-height: 56px; }
  nav {
    height: auto;
    min-height: var(--nav-height);
    padding: 0 0.6rem;
  }
  .nav-inner {
    gap: 0;
    height: 100%;
  }
  .nav-brand { display: none; }
  .nav-links {
    flex: 1;
    justify-content: space-around;
    flex-wrap: wrap;
    gap: 0;
  }
  .nav-links a {
    padding: 0.45rem 0.5rem;
    font-size: 0.8rem;
  }

  .hero { grid-template-columns: 1fr; gap: 1rem; }
  .research-grid { grid-template-columns: 1fr; }
  .cv-item { grid-template-columns: 80px 1fr; gap: 0.75rem; }
  .news-item { grid-template-columns: 64px 1fr; gap: 0.65rem; }
  .pub-filters { gap: 0.4rem; }
  .filter-btn { padding: 0.3rem 0.7rem; }
}

@media (max-width: 380px) {
  nav { padding: 0 0.4rem; }
  .nav-links a { padding: 0.4rem 0.35rem; font-size: 0.78rem; }
  .hero-links { gap: 0.4rem; }
  .news-item {
    grid-template-columns: 1fr;
    gap: 0.15rem;
    padding: 0.7rem 0;
  }
  .news-date { font-size: 0.72rem; }
  .cv-item { grid-template-columns: 70px 1fr; gap: 0.55rem; }
}