:root{
  --paper:#F6F8F6;
  --paper-2:#FFFFFF;
  --ink:#132A2A;
  --ink-soft:#3E5450;
  --muted:#6E827C;
  --line:#DCE4DF;
  --pine:#0F7A5E;
  --pine-deep:#0A5C47;
  --pine-wash:#E7F1EC;
  --oxblood:#7A2E33;
  --radius:14px;
  --maxw:1120px;
  --display:"Space Grotesk", "Pretendard", sans-serif;
  --body:"Pretendard", system-ui, sans-serif;
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:var(--body);
  background:var(--paper);
  color:var(--ink);
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
a{color:inherit;text-decoration:none}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 28px}

/* ---------- LANGUAGE TOGGLE (core mechanism) ---------- */
/* Every text node has both a .ko and .en version; the body class decides which shows. */
body.lang-ko .en{display:none}
body.lang-en .ko{display:none}

/* ---------- NAV ---------- */
header.nav{
  position:sticky;top:0;z-index:50;
  backdrop-filter:saturate(1.1) blur(8px);
  background:rgba(246,248,246,.72);
  border-bottom:1px solid transparent;
  transition:border-color .3s ease, background .3s ease;
}
header.nav.scrolled{border-bottom-color:var(--line);background:rgba(246,248,246,.92)}
.nav-inner{display:flex;align-items:center;justify-content:space-between;height:68px}
.brand{display:flex;align-items:baseline;gap:10px}
.brand .mark{
  font-family:var(--display);font-weight:700;font-size:1.35rem;letter-spacing:-.02em;
  color:var(--ink);
}
.brand .mark .dot{color:var(--pine)}
.brand .sub{font-size:.82rem;color:var(--muted);letter-spacing:.02em}
.nav-right{display:flex;align-items:center;gap:22px}
nav.links{display:flex;gap:28px}
nav.links a{
  font-size:.9rem;color:var(--ink-soft);position:relative;padding:4px 0;font-weight:500;
}
nav.links a::after{
  content:"";position:absolute;left:0;bottom:-2px;height:2px;width:0;background:var(--pine);
  transition:width .25s ease;
}
nav.links a:hover::after,nav.links a:focus-visible::after{width:100%}
.lang-switch{display:inline-flex;border:1px solid var(--line);border-radius:999px;overflow:hidden}
.ls-btn{
  font-family:var(--display);font-size:.76rem;font-weight:600;letter-spacing:.04em;
  padding:6px 13px;background:none;border:0;cursor:pointer;color:var(--muted);
  transition:background .2s,color .2s;
}
.ls-btn[aria-pressed="true"]{background:var(--pine);color:#fff}
.nav-toggle{display:none;background:none;border:0;cursor:pointer;font-size:1.4rem;color:var(--ink)}

/* ---------- HERO ---------- */
.hero{position:relative;overflow:hidden}
.hero-inner{
  display:grid;grid-template-columns:1fr 1fr;gap:40px;align-items:center;
  padding-top:96px;padding-bottom:104px;
}
.eyebrow{
  font-family:var(--display);font-size:.78rem;font-weight:600;letter-spacing:.14em;
  text-transform:uppercase;color:var(--pine-deep);margin-bottom:22px;
  display:inline-flex;align-items:center;gap:9px;
}
.eyebrow::before{content:"";width:26px;height:1.5px;background:var(--pine)}
h1.title{
  font-family:var(--display);font-weight:700;letter-spacing:-.03em;line-height:1.04;
  font-size:clamp(2.5rem,5.4vw,4.15rem);color:var(--ink);
}
h1.title .flip{
  color:var(--pine);
  background:linear-gradient(100deg,var(--pine) 0%, var(--pine-deep) 55%, var(--oxblood) 140%);
  -webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;
}
.lede{
  margin-top:26px;font-size:1.12rem;color:var(--ink-soft);max-width:34em;
  line-height:1.72;
}
.tags{display:flex;flex-direction:column;gap:9px;margin-top:30px}
.tag-row{display:flex;flex-wrap:wrap;gap:9px}
.tag{
  font-size:.82rem;color:var(--ink-soft);background:var(--paper-2);
  border:1px solid var(--line);border-radius:999px;padding:6px 14px;
  transition:border-color .2s, color .2s, transform .2s;
}
.tag:hover{border-color:var(--pine);color:var(--pine-deep);transform:translateY(-1px)}

/* hero image placeholder (user will add their own artwork) */
.signature{position:relative;aspect-ratio:1/1}
.img-placeholder{
  width:100%;height:100%;border:1.5px dashed var(--line);border-radius:18px;
  background:
    repeating-linear-gradient(45deg,transparent,transparent 14px,rgba(15,122,94,.03) 14px,rgba(15,122,94,.03) 28px);
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:6px;
  color:var(--muted);text-align:center;
}
.img-placeholder .ph-title{font-family:var(--display);font-size:.9rem;font-weight:600;letter-spacing:.04em}
.img-placeholder .ph-note{font-size:.78rem;color:var(--muted)}
.signature img{width:100%;height:100%;border-radius:18px;object-fit:cover;display:block}

/* ---------- SECTION SHELL ---------- */
section.block{padding:88px 0;border-top:1px solid var(--line)}
.sec-head{display:flex;align-items:baseline;gap:16px;margin-bottom:44px;flex-wrap:wrap}
.sec-num{
  font-family:var(--display);font-size:.8rem;font-weight:600;color:var(--pine);
  letter-spacing:.08em;
}
.sec-title{
  font-family:var(--display);font-weight:600;letter-spacing:-.02em;
  font-size:clamp(1.7rem,3.2vw,2.3rem);color:var(--ink);
}
.sec-intro{color:var(--ink-soft);max-width:46em;font-size:1.05rem;margin-top:-24px;margin-bottom:44px}

/* ---------- RESEARCH ---------- */
.themes{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}
.theme{
  background:var(--paper-2);border:1px solid var(--line);border-radius:var(--radius);
  padding:26px 24px 28px;transition:transform .22s ease, box-shadow .22s ease, border-color .22s;
}
.theme:hover{transform:translateY(-4px);box-shadow:0 14px 34px -20px rgba(15,122,94,.45);border-color:var(--pine-wash)}
.theme .idx{
  font-family:var(--display);font-size:.78rem;color:var(--pine);font-weight:600;
  letter-spacing:.06em;
}
.theme h3{font-family:var(--display);font-size:1.16rem;font-weight:600;margin:12px 0 6px;letter-spacing:-.01em}
.theme .term{color:var(--muted);font-size:.82rem;font-family:var(--display);letter-spacing:.02em;margin-bottom:12px}
.theme p{font-size:.94rem;color:var(--ink-soft);line-height:1.66}

/* ---------- MEMBERS ---------- */
.pi-card{
  display:grid;grid-template-columns:132px 1fr;gap:30px;align-items:center;
  background:linear-gradient(180deg,var(--pine-wash),var(--paper-2));
  border:1px solid var(--line);border-radius:18px;padding:32px 34px;margin-bottom:44px;
}
.pi-photo{
  width:132px;height:132px;border-radius:16px;
  border:1.5px dashed var(--pine-wash);
  background:rgba(15,122,94,.05);
  display:flex;align-items:center;justify-content:center;
  font-family:var(--display);font-weight:600;color:var(--pine-deep);font-size:.72rem;
  letter-spacing:.04em;text-align:center;line-height:1.4;
  overflow:hidden;
}
.pi-photo img{width:100%;height:100%;border-radius:16px;object-fit:cover;display:block}
.pi-info .role{font-family:var(--display);font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:var(--pine-deep);font-weight:600}
.pi-info h3{font-size:1.55rem;font-family:var(--display);font-weight:600;margin:6px 0 2px;letter-spacing:-.01em}
.pi-info h3 .pi-sub{font-size:1rem;color:var(--muted);font-weight:400}
.pi-info .aff{color:var(--ink-soft);font-size:.98rem}
.pi-info .pi-int{color:var(--muted);font-size:.9rem;margin-top:10px}
.pi-info .pi-mail{display:inline-block;margin-top:12px;font-size:.86rem;color:var(--pine-deep);border-bottom:1px solid var(--pine-wash);padding-bottom:1px}

.subhead{font-family:var(--display);font-size:.82rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin:0 0 18px;font-weight:600}
.people{display:grid;grid-template-columns:repeat(4,1fr);gap:16px;margin-bottom:40px}
.person{background:var(--paper-2);border:1px solid var(--line);border-radius:12px;padding:20px 18px;transition:border-color .2s,transform .2s}
.person:hover{border-color:var(--pine);transform:translateY(-2px)}
.avatar{
  width:55px;height:55px;border-radius:50%;
  border:1.5px dashed var(--line);background:var(--pine-wash);
  margin-bottom:14px;
}
.avatar img{width:100%;height:100%;border-radius:50%;object-fit:cover;display:block}
.person .nm{font-weight:600;font-size:1rem}
.person .pos{color:var(--muted);font-size:.84rem;margin-top:2px}
.person .person-mail{display:inline-block;margin-top:8px;font-size:.78rem;color:var(--pine-deep);border-bottom:1px solid var(--pine-wash);padding-bottom:1px}

/* ---------- PI BIOGRAPHY ---------- */
.bio-list{list-style:none;display:flex;flex-direction:column;gap:12px;margin-bottom:40px}
.bio-item{display:flex;gap:18px;font-size:.94rem;line-height:1.5}
.bio-item .yr{font-family:var(--display);font-weight:600;color:var(--pine);font-size:.86rem;min-width:110px;padding-top:1px}
.bio-item .desc{color:var(--ink-soft)}

/* ---------- PUBLICATIONS ---------- */
.pub-year{display:flex;gap:26px;padding:22px 0;border-bottom:1px solid var(--line);align-items:flex-start}
.pub-year:first-of-type{border-top:1px solid var(--line)}
.pub-y{font-family:var(--display);font-weight:600;font-size:1.35rem;color:var(--pine);min-width:70px;padding-top:2px}
.pub-items{flex:1;display:flex;flex-direction:column;gap:18px}
.pub{font-size:.98rem;line-height:1.6}
.pub .t{font-weight:600;color:var(--ink)}
.pub .a{color:var(--ink-soft);font-size:.92rem}
.pub .a .me{color:var(--pine-deep);font-weight:600}
.pub .j{color:var(--muted);font-size:.88rem;font-style:italic}

/* ---------- FOOTER ---------- */
footer{background:var(--ink);color:#cfe0da;padding:60px 0 44px}
.foot-grid{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:36px}
footer .fmark{font-family:var(--display);font-weight:700;font-size:1.3rem;color:#fff;letter-spacing:-.02em}
footer .fmark .dot{color:#41c79e}
footer .fko{color:#8fb0a6;font-size:.86rem;margin-top:6px}
footer p.desc{color:#a7c3ba;font-size:.92rem;margin-top:14px;max-width:26em;line-height:1.7}
footer h4{font-family:var(--display);font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:#6fa494;margin-bottom:14px}
footer ul{list-style:none}
footer li{font-size:.92rem;margin-bottom:9px;color:#bdd4cc}
footer a:hover{color:#fff}
.foot-base{border-top:1px solid rgba(255,255,255,.1);margin-top:40px;padding-top:22px;font-size:.82rem;color:#7fa093;display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px}

/* reveal */
.reveal{opacity:0;transform:translateY(18px);transition:opacity .7s ease, transform .7s ease}
.reveal.in{opacity:1;transform:none}

/* ---------- RESPONSIVE ---------- */
@media(max-width:900px){
  .hero-inner{grid-template-columns:1fr;padding-top:70px;padding-bottom:76px}
  .signature{order:-1;max-width:420px}
  .themes{grid-template-columns:repeat(2,1fr)}
  .people{grid-template-columns:repeat(2,1fr)}
  .foot-grid{grid-template-columns:1fr 1fr}
}
@media(max-width:620px){
  nav.links{display:none}
  .nav-toggle{display:block}
  .themes{grid-template-columns:1fr}
  .people{grid-template-columns:1fr 1fr}
  .pi-card{grid-template-columns:1fr;text-align:center;justify-items:center}
  .pub-year{flex-direction:column;gap:10px}
  .foot-grid{grid-template-columns:1fr}
  .brand .sub{display:none}
  .bio-item{flex-direction:column;gap:2px}
}
@media(prefers-reduced-motion:reduce){
  *{scroll-behavior:auto!important}
  .reveal{opacity:1;transform:none;transition:none}
}
:focus-visible{outline:2.5px solid var(--pine);outline-offset:3px;border-radius:4px}