/* ── Variables ──────────────────────────────────────────────────── */
:root,
[data-theme="light"] {
  --illini-navy:   #13294B;
  --illini-orange: #FF5F05;
  --text:          #212529;
  --text-light:    #6c757d;
  --bg:            #ffffff;
  --bg-nav:        rgba(255, 255, 255, 0.85);
  --link:          #0076df;
  --border:        #e9ecef;
  --card-bg:       #f8f9fa;
  --tag-bg:        transparent;
  --tag-border:    var(--illini-navy);
  --tag-color:     var(--illini-navy);
  --shadow:        0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-nav:    0 1px 8px rgba(0, 0, 0, 0.08);
  --max-width:     860px;
  --section-gap:   3.5rem;
  --nav-height:    52px;
  --progress-color: var(--illini-navy);
}

[data-theme="dark"] {
  --illini-navy:   #8ab4f8;
  --illini-orange: #ff8a50;
  --text:          #e0e0e0;
  --text-light:    #9e9e9e;
  --bg:            #1a1a2e;
  --bg-nav:        rgba(26, 26, 46, 0.9);
  --link:          #4da3ff;
  --border:        #2d2d4a;
  --card-bg:       #22223a;
  --tag-bg:        transparent;
  --tag-border:    #8ab4f8;
  --tag-color:     #8ab4f8;
  --shadow:        0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-nav:    0 1px 8px rgba(0, 0, 0, 0.4);
  --progress-color: #4da3ff;
}

/* ── Reset & base ───────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-weight: 400;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
  padding: 0;
  transition: background 0.3s ease, color 0.3s ease;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: calc(var(--nav-height) + 1rem) 1.25rem 4rem;
}

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

/* ── Progress bar ──────────────────────────────────────────────── */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 2.5px;
  width: 0%;
  background: var(--progress-color);
  z-index: 1001;
  transition: width 0.1s linear;
}

/* ── Navbar ─────────────────────────────────────────────────────── */
.navbar {
  position: fixed;
  top: 2.5px;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: var(--bg-nav);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 1000;
  transition: box-shadow 0.3s ease, background 0.3s ease;
}

.navbar.scrolled {
  box-shadow: var(--shadow-nav);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.25rem;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.3px;
}
.nav-brand:hover { text-decoration: none; color: var(--link); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.4rem;
}

.nav-link {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-light);
  position: relative;
  transition: color 0.2s ease;
}

.nav-link:hover {
  color: var(--text);
  text-decoration: none;
}

.nav-link.active {
  color: var(--text);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--progress-color);
  border-radius: 1px;
}

/* ── Theme toggle ──────────────────────────────────────────────── */
.theme-toggle {
  background: none;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  color: var(--text-light);
  cursor: pointer;
  padding: 5px 8px;
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color 0.2s, border-color 0.2s, background 0.2s;
  margin-left: 0.5rem;
}

.theme-toggle:hover {
  color: var(--text);
  border-color: var(--text-light);
  background: var(--card-bg);
}

/* ── Bio ─────────────────────────────────────────────────────────── */
.bio { padding-top: 0.5rem; }

.bio-inner {
  display: flex;
  gap: 2.5rem;
  align-items: flex-start;
}

.bio-text { flex: 1; }

.bio-text h1 {
  font-size: 2rem;
  font-weight: 600;
  letter-spacing: -0.5px;
  margin-bottom: 0.1rem;
}

.korean-name {
  font-family: 'Noto Sans KR', sans-serif;
  font-weight: 400;
  font-size: 0.9rem;
  color: var(--text-light);
  letter-spacing: 0.04em;
  margin-bottom: 0.25rem;
}

.tagline {
  font-size: 0.92rem;
  font-style: italic;
  color: var(--text-light);
  margin-bottom: 0.8rem;
}

.bio-photo {
  flex-shrink: 0;
  width: 180px;
}

.bio-photo img {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  display: block;
  border: 3px solid var(--border);
  box-shadow: var(--shadow);
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.bio-photo img:hover {
  border-color: var(--text-light);
}

.bio-text p {
  margin-bottom: 0.85rem;
  font-size: 0.95rem;
}

/* ── Keyword tags ───────────────────────────────────────────────── */
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0.65rem 0;
}

.tag {
  padding: 3px 12px;
  border-radius: 20px;
  border: 1.5px solid var(--tag-border);
  background: var(--tag-bg);
  color: var(--tag-color);
  font-size: 0.78rem;
  font-weight: 500;
  line-height: 1.7;
  transition: background 0.2s, color 0.2s, border-color 0.2s;
}

/* ── Internship note ────────────────────────────────────────────── */
.bio-text p.internship-note { font-size: 0.82rem; margin-bottom: 0.5rem; }
.bio-text p.internship-note strong { color: var(--illini-orange); font-weight: 500; }

/* ── Social icons ───────────────────────────────────────────────── */
.socials { display: flex; gap: 0.9rem; font-size: 1.2rem; margin-top: 0.4rem; }

.socials a {
  color: var(--text-light);
  transition: color 0.2s ease, transform 0.2s ease;
}
.socials a:hover {
  color: var(--link);
  text-decoration: none;
  transform: translateY(-1px);
}

/* ── Sections ───────────────────────────────────────────────────── */
section { margin-top: var(--section-gap); }

section h2 {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 1.1rem;
  padding-bottom: 0.35rem;
  border-bottom: 1px solid var(--border);
}

/* ── News ───────────────────────────────────────────────────────── */
.news-list {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.news-item {
  font-size: 0.9rem;
  display: flex;
  gap: 0.75rem;
  align-items: baseline;
}

.news-date {
  color: var(--text-light);
  font-size: 0.82rem;
  flex-shrink: 0;
  min-width: 70px;
}

.news-content { flex: 1; }

/* ── Talks & Teaching ───────────────────────────────────────────── */
.talk { display: flex; align-items: flex-start; gap: 0.75rem; margin-bottom: 1rem; }

.badge {
  flex-shrink: 0;
  display: inline-block;
  padding: 2px 10px;
  border-radius: 4px;
  color: white;
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-top: 3px;
  white-space: nowrap;
}

.badge-instructor  { background: var(--illini-orange); }
.badge-presentation { background: #13294B; }
[data-theme="dark"] .badge-presentation { background: #3a5a8a; }
.badge-mentor      { background: #2D6A4F; }
[data-theme="dark"] .badge-mentor { background: #52B788; }
.badge-book        { background: #6A4C93; }
[data-theme="dark"] .badge-book { background: #9D7BC4; }

.talk-body { font-size: 0.88rem; line-height: 1.5; flex: 1; min-width: 0; }
.talk-body strong { font-weight: 500; }
.talk-body em { color: var(--text-light); font-style: normal; font-size: 0.84rem; }

/* ── Publications ───────────────────────────────────────────────── */
.pub-section-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.8rem;
  margin-top: 1.5rem;
}

.pub-section-title:first-of-type { margin-top: 0; }

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

.pub-item {
  margin-bottom: 1.4rem;
  padding: 1rem 1.1rem;
  background: var(--card-bg);
  border-radius: 8px;
  border: 1px solid var(--border);
  transition: background 0.3s ease, border-color 0.3s ease, box-shadow 0.2s ease;
}

.pub-item:hover {
  box-shadow: var(--shadow);
}

.pub-item .pub-title {
  font-size: 0.93rem;
  font-weight: 500;
  color: var(--link);
  display: block;
  margin-bottom: 0.2rem;
}

.pub-item .pub-title:hover { text-decoration: none; }

.pub-authors {
  font-size: 0.85rem;
  color: var(--text-light);
  margin-bottom: 0.15rem;
}

.pub-authors .self { font-weight: 600; color: var(--text); }

.pub-badges { display: flex; gap: 0.4rem; margin-top: 0.35rem; flex-wrap: wrap; }

.pub-badge {
  display: inline-block;
  padding: 1px 8px;
  border-radius: 3px;
  font-size: 0.72rem;
  font-weight: 600;
}

.pub-badge-venue {
  background: #f0f4f8;
  color: #13294B;
  border: 1px solid #d0daea;
}
[data-theme="dark"] .pub-badge-venue {
  background: #2a2a4a;
  color: #8ab4f8;
  border-color: #3d3d6a;
}

.pub-badge-submitted {
  background: #fff4e5;
  color: #b75d00;
  border: 1px solid #ffd9a8;
  font-style: italic;
}
[data-theme="dark"] .pub-badge-submitted {
  background: #3a2a1a;
  color: #ffb366;
  border-color: #5a3a1a;
}

.pub-badge-review {
  background: #e8f4fd;
  color: #0a558c;
  border: 1px solid #b6d4fe;
  font-style: italic;
}
[data-theme="dark"] .pub-badge-review {
  background: #1a2a3a;
  color: #79b8ff;
  border-color: #2a4a6a;
}

.pub-badge-oral {
  background: #edf7ed;
  color: #2d7a2d;
  border: 1px solid #b2dfb2;
  font-weight: 700;
}
[data-theme="dark"] .pub-badge-oral {
  background: #1a3a1a;
  color: #66cc66;
  border-color: #2d5a2d;
}

.pub-badge-poster {
  background: #f0f0f0;
  color: #555;
  border: 1px solid #d0d0d0;
}
[data-theme="dark"] .pub-badge-poster {
  background: #2a2a3a;
  color: #aaa;
  border-color: #3d3d5a;
}

.pub-links {
  display: flex;
  gap: 0.7rem;
  margin-top: 0.4rem;
}

.pub-links a {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--link);
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  padding: 2px 8px;
  border-radius: 4px;
  border: 1px solid var(--border);
  transition: background 0.2s, border-color 0.2s;
}

.pub-links a:hover {
  background: var(--card-bg);
  border-color: var(--link);
  text-decoration: none;
}

.pub-note {
  font-size: 0.78rem;
  color: var(--text-light);
  margin-top: 0.15rem;
}

.pub-links {
  display: flex;
  gap: 0.4rem;
  margin-top: 0.35rem;
}

.pub-link {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.15rem 0.5rem;
  border: 1px solid var(--accent);
  border-radius: 3px;
  color: var(--accent);
  text-decoration: none;
  transition: background 0.2s, color 0.2s;
}

.pub-link:hover {
  background: var(--accent);
  color: #fff;
}

.pub-more {
  font-size: 0.85rem;
  color: var(--text-light);
  margin-top: 0.5rem;
}

/* ── Awards ─────────────────────────────────────────────────────── */
.award-item { display: flex; gap: 0.65rem; align-items: flex-start; margin-bottom: 0.8rem; }
.award-icon { color: var(--illini-orange); margin-top: 3px; font-size: 0.9rem; flex-shrink: 0; width: 1.1rem; text-align: center; }
.award-body { font-size: 0.92rem; }
.award-body strong { font-weight: 500; }
.award-meta { font-size: 0.85rem; color: var(--text-light); }

/* ── Education ──────────────────────────────────────────────────── */
.edu-list { list-style: none; }

.edu-item { margin-bottom: 1.1rem; display: flex; gap: 0.65rem; align-items: flex-start; }

.edu-icon { color: var(--text-light); margin-top: 3px; font-size: 0.9rem; flex-shrink: 0; width: 1.1rem; text-align: center; }

.edu-body { font-size: 0.92rem; }
.edu-body strong { font-weight: 500; }
.edu-meta { font-size: 0.85rem; color: var(--text-light); }

/* ── Footer ─────────────────────────────────────────────────────── */
footer {
  margin-top: 4rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
  font-size: 0.8rem;
  color: var(--text-light);
  transition: border-color 0.3s ease;
}

/* ── Responsive ─────────────────────────────────────────────────── */
@media (max-width: 600px) {
  .bio-inner { flex-direction: column; align-items: center; text-align: center; }
  .bio-photo { width: 140px; }
  .bio-photo img { width: 140px; height: 140px; }
  .bio-text h1 { font-size: 1.6rem; }
  .tags { justify-content: center; }
  .socials { justify-content: center; }
  .internship-note { text-align: center; }

  .nav-links { gap: 0.8rem; }
  .nav-link { font-size: 0.75rem; }
  .nav-brand { font-size: 0.85rem; }

  .pub-item { padding: 0.8rem; }

  .news-item { flex-direction: column; gap: 0.15rem; }
}

@media (max-width: 400px) {
  .nav-links { gap: 0.5rem; }
  .nav-link { font-size: 0.7rem; }
}