:root {
  --navy: #0b2a4a;
  --blue: #1565c0;
  --teal: #12a3b4;
  --orange: #f37321;
  --ink: #1d2733;
  --muted: #5b6b7c;
  --line: #e3e8ee;
  --bg: #ffffff;
  --bg-soft: #f5f8fb;
  --radius: 14px;
  --shadow: 0 6px 24px rgba(11, 42, 74, 0.08);
  --max: 1160px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }
body {
  margin: 0;
  font-family: "Pretendard", -apple-system, BlinkMacSystemFont, "Segoe UI", "Malgun Gothic", sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  word-break: keep-all;
}
img { max-width: 100%; display: block; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 20px; }

/* ---------- header ---------- */
header.site {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
header.site .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--navy); font-weight: 800; letter-spacing: 0.5px; }
.brand img { height: 40px; }
.brand span { font-size: 15px; line-height: 1.2; }
.brand small { display: block; font-weight: 500; font-size: 11px; color: var(--muted); letter-spacing: 0; }
nav.main ul { list-style: none; display: flex; gap: 22px; margin: 0; padding: 0; }
nav.main a { color: var(--ink); font-weight: 600; font-size: 15px; }
.brand span, nav.main a { white-space: nowrap; }
@media (max-width: 1180px) and (min-width: 821px) { .brand span { display: none; } nav.main ul { gap: 16px; } }
nav.main a:hover { color: var(--blue); text-decoration: none; }
.head-right { display: flex; align-items: center; gap: 18px; }
.lang { display: flex; border: 1px solid var(--line); border-radius: 999px; padding: 2px; background: var(--bg-soft); }
.lang a { padding: 4px 10px; border-radius: 999px; font-size: 13px; font-weight: 700; color: var(--muted); }
.lang a:hover { text-decoration: none; color: var(--navy); }
.lang a.on { background: var(--navy); color: #fff; }
.menu-btn { display: none; background: none; border: 0; font-size: 26px; color: var(--navy); cursor: pointer; }

/* ---------- hero ---------- */
.hero {
  position: relative; color: #fff;
  background: linear-gradient(100deg, rgba(8, 30, 56, 0.92) 0%, rgba(8, 30, 56, 0.72) 45%, rgba(8, 30, 56, 0.25) 100%),
              url("assets/img/hero.jpg") center/cover no-repeat;
  padding: 120px 0 110px;
}
.hero .eyebrow { color: #ffb37a; font-weight: 700; letter-spacing: 1px; font-size: 14px; text-transform: uppercase; }
.hero h1 { font-size: clamp(30px, 5vw, 52px); line-height: 1.15; margin: 12px 0 8px; }
.hero .ko { font-size: clamp(18px, 2.4vw, 24px); font-weight: 600; opacity: 0.95; }
.hero .tagline { margin-top: 18px; font-size: 18px; color: #cfe3ff; }
.hero .btns { margin-top: 32px; display: flex; flex-wrap: wrap; gap: 12px; }
.btn { display: inline-block; padding: 12px 22px; border-radius: 999px; font-weight: 700; font-size: 15px; }
.btn.primary { background: var(--orange); color: #fff; }
.btn.ghost { border: 1.5px solid rgba(255, 255, 255, 0.7); color: #fff; }
.btn:hover { text-decoration: none; filter: brightness(1.08); }
.btn.outline { border: 1.5px solid var(--navy); color: var(--navy); background: #fff; }
.pi-links { display: flex; justify-content: center; gap: 14px; margin-top: 10px; font-size: 14px; font-weight: 600; }
.cv-dl { display: flex; flex-direction: column; gap: 8px; margin-top: 16px; }
.cv-dl .btn { text-align: center; padding: 10px 16px; font-size: 14px; }

/* ---------- sections ---------- */
section { padding: 88px 0; }
section.soft { background: var(--bg-soft); }
.sec-head { margin-bottom: 40px; }
.sec-head .en { color: var(--orange); font-weight: 800; font-size: 14px; letter-spacing: 1.5px; text-transform: uppercase; }
.sec-head h2 { font-size: clamp(26px, 3.4vw, 36px); margin: 6px 0 10px; color: var(--navy); }
.sec-head p { color: var(--muted); max-width: 760px; margin: 0; }

.quote {
  font-size: clamp(18px, 2.2vw, 22px); font-weight: 700; color: var(--blue);
  border-left: 4px solid var(--orange); padding: 6px 0 6px 18px; margin: 0 0 36px;
}

/* stats */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-top: 36px; }
.stat { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; text-align: center; }
.stat b { display: block; font-size: 34px; color: var(--navy); line-height: 1.1; }
.stat span { color: var(--muted); font-size: 14px; }

/* philosophy flow */
.flow { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
.flow .step { position: relative; background: #fff; border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; }
.flow .step h3 { margin: 0; padding: 14px 16px; color: #fff; font-size: 17px; }
.flow .step:nth-child(1) h3 { background: #3c9a3c; }
.flow .step:nth-child(2) h3 { background: var(--teal); }
.flow .step:nth-child(3) h3 { background: var(--blue); }
.flow .step:nth-child(4) h3 { background: var(--navy); }
.flow .step ul { margin: 0; padding: 14px 16px 18px 34px; color: var(--muted); font-size: 15px; }
.flow .step:not(:last-child)::after {
  content: ""; position: absolute; right: -14px; top: 18px; width: 0; height: 0;
  border-top: 10px solid transparent; border-bottom: 10px solid transparent; border-left: 10px solid var(--orange);
}
.physics-tags { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 28px; }
.tag { background: #e8f1fb; color: var(--blue); padding: 6px 14px; border-radius: 999px; font-weight: 600; font-size: 14px; }

/* research cards */
.research-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.rcard { background: #fff; border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; display: flex; flex-direction: column; }
.rcard .img { background: #fff; height: 220px; display: flex; align-items: center; justify-content: center; border-bottom: 1px solid var(--line); padding: 12px; }
.rcard .img img { max-height: 100%; object-fit: contain; }
.rcard .body { padding: 22px 24px 26px; }
.rcard .num { color: var(--orange); font-weight: 800; font-size: 13px; letter-spacing: 1px; }
.rcard h3 { margin: 4px 0 2px; font-size: 20px; color: var(--navy); }
.rcard .sub { color: var(--muted); font-size: 14px; margin-bottom: 12px; }
.rcard ul { margin: 0; padding-left: 20px; font-size: 15px; }
.rcard li { margin: 3px 0; }
.rcard .kpi { margin-top: 14px; display: flex; flex-wrap: wrap; gap: 8px; }
.rcard .kpi span { background: #fff4ec; color: #b4520f; border-radius: 8px; padding: 4px 10px; font-size: 13px; font-weight: 700; }

/* timeline */
.timeline { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-top: 56px; }
.tl { border-top: 4px solid var(--teal); background: #fff; border-radius: 0 0 var(--radius) var(--radius); padding: 18px; box-shadow: var(--shadow); }
.tl:nth-child(1) { border-color: #3c9a3c; }
.tl:nth-child(3) { border-color: var(--blue); }
.tl:nth-child(4) { border-color: var(--navy); }
.tl .yr { font-size: 13px; color: var(--muted); font-weight: 700; }
.tl h4 { margin: 2px 0 8px; font-size: 17px; color: var(--navy); }
.tl p { margin: 0; font-size: 14px; color: var(--muted); }
.tl img { height: 110px; margin: 12px auto 0; object-fit: contain; }

/* highlights */
.hl-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.hl { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; }
.hl .img { height: 260px; display: flex; align-items: center; justify-content: center; background: #fff; padding: 10px; }
.hl .img img { max-height: 100%; object-fit: contain; }
.hl .cap { padding: 16px 20px 20px; border-top: 1px solid var(--line); }
.hl .cap b { color: var(--navy); }
.hl .cap p { margin: 4px 0 0; color: var(--muted); font-size: 14px; }

/* vision */
.vision { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.vcard { border-radius: var(--radius); overflow: hidden; background: #fff; box-shadow: var(--shadow); }
.vcard .top { padding: 14px 18px; color: #fff; }
.vcard:nth-child(1) .top { background: #3c9a3c; }
.vcard:nth-child(2) .top { background: var(--teal); }
.vcard:nth-child(3) .top { background: var(--blue); }
.vcard .top small { display: block; opacity: 0.9; font-weight: 600; }
.vcard .top b { font-size: 19px; }
.vcard img { height: 170px; width: 100%; object-fit: cover; }
.vcard .img-contain { object-fit: contain; background: #fff; padding: 8px; }
.vcard .credit { font-size: 11px; color: var(--muted); text-align: right; padding: 4px 12px 0; }
.vcard ul { margin: 0; padding: 16px 18px 20px 36px; font-size: 15px; }

/* PI */
.pi { display: grid; grid-template-columns: 260px 1fr; gap: 40px; align-items: start; }
.pi .photo { border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); }
.pi .name { margin-top: 16px; text-align: center; }
.pi .name b { font-size: 22px; color: var(--navy); }
.pi .name span { display: block; color: var(--muted); font-size: 14px; }
.cv { display: grid; grid-template-columns: 1fr 1fr; gap: 28px 36px; }
.cv h3 { margin: 0 0 8px; font-size: 16px; color: var(--blue); border-bottom: 2px solid var(--line); padding-bottom: 6px; }
.cv ul { list-style: none; margin: 0; padding: 0; font-size: 15px; }
.cv li { padding: 3px 0; }
.cv li .y { color: var(--muted); font-size: 13px; margin-left: 4px; }
.cv li .sub { color: var(--muted); font-size: 13px; }

/* publications */
.pub-tools { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.pub-tools button {
  border: 1px solid var(--line); background: #fff; padding: 7px 14px; border-radius: 999px;
  font-size: 14px; font-weight: 600; cursor: pointer; color: var(--ink); font-family: inherit;
}
.pub-tools button.on { background: var(--navy); color: #fff; border-color: var(--navy); }
.pub-tools .cnt { margin-left: 6px; font-weight: 700; color: var(--orange); }
.pub-tools button.on .cnt { color: #ffb37a; }
ol.pubs { list-style: none; margin: 0; padding: 0; counter-reset: none; }
ol.pubs li { display: grid; grid-template-columns: 48px 1fr auto; gap: 12px; align-items: baseline; padding: 12px 4px; border-bottom: 1px solid var(--line); font-size: 15px; }
ol.pubs .no { color: var(--muted); font-weight: 700; }
ol.pubs .t { display: block; font-weight: 700; color: var(--navy); }
ol.pubs .a { display: block; font-size: 14px; color: var(--muted); margin: 2px 0; }
ol.pubs .a b { color: var(--ink); }
ol.pubs .j { font-style: italic; }
ol.pubs .v { color: var(--muted); }
ol.pubs .yr { color: var(--muted); font-size: 14px; }
.badge { display: inline-block; font-size: 11px; font-weight: 800; padding: 2px 8px; border-radius: 6px; margin-left: 6px; vertical-align: 1px; }
.badge.main { background: #fff1e6; color: #c25510; }
.badge.rev { background: #eef2f7; color: var(--muted); }
.note { font-size: 13px; color: var(--muted); margin-top: 16px; }

/* network / teaching */
.two { display: grid; grid-template-columns: 1fr 1fr; gap: 28px; }
.box { background: #fff; border-radius: var(--radius); box-shadow: var(--shadow); padding: 24px 26px; }
.box h3 { margin: 0 0 12px; color: var(--navy); font-size: 19px; }
.box dl { margin: 0; }
.box dt { font-weight: 700; color: var(--blue); margin-top: 10px; font-size: 15px; }
.box dd { margin: 2px 0 0; font-size: 15px; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chips span { border: 1px solid var(--line); border-radius: 8px; padding: 6px 12px; font-size: 14px; background: var(--bg-soft); }
.tiers { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin-top: 16px; }
.tiers div { border-radius: 10px; padding: 12px; color: #fff; font-size: 14px; }
.tiers div b { display: block; font-size: 15px; }
.tiers div:nth-child(1) { background: #3c9a3c; }
.tiers div:nth-child(2) { background: var(--teal); }
.tiers div:nth-child(3) { background: var(--blue); }

/* members */
.members { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.mem { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; text-align: center; }
.mem .ph { width: 96px; height: 96px; border-radius: 50%; margin: 0 auto 12px; background: var(--bg-soft); overflow: hidden; display: flex; align-items: center; justify-content: center; color: #b8c4d0; font-size: 40px; }
.mem .ph img { width: 100%; height: 100%; object-fit: cover; }
.mem b { display: block; color: var(--navy); }
.mem span { font-size: 14px; color: var(--muted); }
.mem.open { border-style: dashed; border-color: var(--orange); }
.mem.open b { color: var(--orange); }

/* join */
.join { background: linear-gradient(120deg, var(--navy), #13457a); color: #fff; border-radius: 20px; padding: 44px; display: grid; grid-template-columns: 1.2fr 1fr; gap: 36px; }
.join h2 { margin: 0 0 10px; font-size: 30px; }
.join p { color: #d5e4f5; margin: 0 0 8px; }
.join ul { margin: 12px 0 0; padding-left: 20px; color: #eaf2fb; }
.join .side { background: rgba(255, 255, 255, 0.08); border-radius: 14px; padding: 22px; }
.join .side h3 { margin: 0 0 8px; font-size: 17px; color: #ffb37a; }

/* contact / footer */
.contact { display: grid; grid-template-columns: 1fr 1fr; gap: 28px; }
.contact .box p { margin: 6px 0; }
.map { border: 0; width: 100%; height: 300px; border-radius: var(--radius); }
footer { background: #071d33; color: #9fb3c8; padding: 30px 0; font-size: 14px; }
footer .wrap { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px; }

/* ---------- responsive ---------- */
@media (max-width: 980px) {
  .stats, .timeline, .members { grid-template-columns: repeat(2, 1fr); }
  .flow { grid-template-columns: repeat(2, 1fr); }
  .flow .step::after { display: none; }
  .vision { grid-template-columns: 1fr; }
}
@media (max-width: 820px) {
  nav.main { display: none; position: absolute; top: 64px; left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--line); }
  nav.main.open { display: block; }
  nav.main ul { flex-direction: column; gap: 0; padding: 8px 20px 16px; }
  nav.main a { display: block; padding: 10px 0; }
  .menu-btn { display: block; }
  .research-grid, .hl-grid, .two, .contact, .join, .cv { grid-template-columns: 1fr; }
  .pi { grid-template-columns: 1fr; }
  .pi .photo { max-width: 220px; margin: 0 auto; }
  section { padding: 64px 0; }
  .join { padding: 28px; }
}
@media (max-width: 520px) {
  .brand span { display: none; }
  .wrap { padding: 0 16px; }
  .stats, .timeline, .members, .flow, .tiers { grid-template-columns: 1fr; }
  ol.pubs li { grid-template-columns: 36px 1fr; }
  ol.pubs .yr { grid-column: 2; }
  .hero { padding: 84px 0 76px; }
}