/* ──────────────────────────────────────────────
   Fonts — Noto Sans KR (한글) · Inter (Latin)
   ────────────────────────────────────────────── */

/* ──────────────────────────────────────────────
   Tokens
   ────────────────────────────────────────────── */
:root {
  --bg:        #f6f6f4;
  --surface:   #ffffff;
  --border:    #e4e4e0;
  --border-2:  #ccccc6;
  --text:      #1a1a18;
  --text-2:    #3d3d38;
  --muted:     #888882;
  --tag-bg:    #ededeb;
  --tag-text:  #5a5a54;

  --r:         10px;
  --r-full:    9999px;

  --shadow-card:       0 1px 2px rgba(0,0,0,0.04), 0 3px 10px rgba(0,0,0,0.05);
  --shadow-card-hover: 0 4px 8px rgba(0,0,0,0.06), 0 14px 32px rgba(0,0,0,0.09);

  --max-w: 1040px;
  --px: clamp(1.25rem, 5vw, 2.5rem);
}

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

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

body {
  font-family: "Inter", "Noto Sans KR", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a   { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
button { font-family: inherit; cursor: pointer; }

/* ──────────────────────────────────────────────
   Layout
   ────────────────────────────────────────────── */
.container {
  max-width: var(--max-w);
  margin-inline: auto;
  padding-inline: var(--px);
}

/* ──────────────────────────────────────────────
   Header
   ────────────────────────────────────────────── */
.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(246, 246, 244, 0.88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}

.header__inner {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  height: 54px;
}

.header__logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-shrink: 0;
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: var(--text);
  color: #fff;
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.logo-name {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.01em;
}

/* Tab Nav */
.tab-nav {
  display: flex;
  align-items: center;
  gap: 2px;
  flex: 1;
}

.tab-btn {
  padding: 0.35rem 0.85rem;
  border-radius: var(--r-full);
  border: none;
  background: transparent;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--muted);
  transition: background 0.15s, color 0.15s;
  white-space: nowrap;
}

.tab-btn:hover  { background: var(--tag-bg); color: var(--text-2); }
.tab-btn.active { background: var(--text); color: #fff; font-weight: 600; }

.header__contact {
  flex-shrink: 0;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--muted);
  transition: color 0.15s;
}
.header__contact:hover { color: var(--text); }

/* ──────────────────────────────────────────────
   Hero
   ────────────────────────────────────────────── */
.hero {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.hero__inner {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(260px, 0.75fr);
  align-items: center;
  gap: 2rem;
  padding-block: 2.75rem;
}

.hero__text {
  min-width: 0;
}

.hero__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 1rem;
}

.hero__tags span {
  padding: 0.28rem 0.7rem;
  border-radius: var(--r-full);
  border: 1px solid var(--border);
  background: var(--bg);
  font-size: 0.76rem;
  font-weight: 500;
  color: var(--text-2);
}

.hero__bio {
  max-width: 24rem;
  font-size: 0.875rem;
  line-height: 1.85;
  color: var(--muted);
}

.hero__contact {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 0.85rem;
  margin-top: 1.4rem;
}

.hero__contact a {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--muted);
  border-bottom: 1px solid transparent;
  padding-bottom: 1px;
  transition: color 0.15s, border-color 0.15s;
}
.hero__contact a:hover { color: var(--text); border-color: var(--border-2); }

.hero__profile {
  width: 100%;
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: var(--r);
  background: var(--bg);
  box-shadow: var(--shadow-card);
}

.hero__profile img {
  width: 100%;
  aspect-ratio: 1881 / 836;
  object-fit: cover;
  object-position: center;
}

/* ──────────────────────────────────────────────
   Main / Panels
   ────────────────────────────────────────────── */
.main { padding: 2.5rem 0 5rem; }

.panel         { display: none; }
.panel.active  { display: block; }

.panel__header {
  display: flex;
  align-items: baseline;
  gap: 1.25rem;
  padding-bottom: 1.5rem;
  margin-bottom: 1.75rem;
  border-bottom: 1px solid var(--border);
}

.panel__header h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.01em;
  white-space: nowrap;
}

.panel__header p {
  font-size: 0.85rem;
  color: var(--muted);
}

/* ──────────────────────────────────────────────
   Card Grid
   ────────────────────────────────────────────── */
.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.research-stack {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.research-row {
  display: grid;
  gap: 1rem;
  justify-content: start;
}

.research-row--articles {
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  width: 100%;
}

.research-row--single {
  grid-template-columns: minmax(260px, 320px);
}

.research-row--double {
  grid-template-columns: repeat(2, minmax(260px, 320px));
}

/* ──────────────────────────────────────────────
   Card (no image)
   ────────────────────────────────────────────── */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-card-hover);
  border-color: var(--border-2);
}

.card__body {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  padding: 1.5rem;
}

.tag {
  display: inline-block;
  width: fit-content;
  padding: 0.18rem 0.55rem;
  border-radius: var(--r-full);
  background: var(--tag-bg);
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--tag-text);
}

.card__body h3 {
  font-family: "Noto Sans KR", "Inter", sans-serif;
  font-size: 0.975rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
  letter-spacing: -0.01em;
}

.card__body p {
  font-size: 0.83rem;
  color: var(--muted);
  line-height: 1.75;
  flex: 1;
}

.card__body a {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  margin-top: 0.5rem;
  width: fit-content;
  padding: 0.45rem 1rem;
  border-radius: var(--r-full);
  background: var(--text);
  color: #fff;
  font-size: 0.73rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  transition: background 0.15s;
}

.card__body a::after { content: "→"; font-size: 0.85em; }
.card__body a:hover  { background: #333; }

/* ──────────────────────────────────────────────
   Feature Card (AI 탭 — READgrow)
   ────────────────────────────────────────────── */
.feature-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 3rem;
  padding: 2.5rem 2.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
}

.feature-card__left {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
  max-width: 36rem;
}

.feature-card__left h3 {
  font-family: "Noto Sans KR", "Inter", sans-serif;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
}

.feature-card__left p {
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.8;
}

.feature-card__link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  flex-shrink: 0;
  padding: 0.7rem 1.5rem;
  border-radius: var(--r-full);
  background: var(--text);
  color: #fff;
  font-size: 0.85rem;
  font-weight: 600;
  white-space: nowrap;
  transition: background 0.15s;
}
.feature-card__link:hover { background: #333; }

/* ──────────────────────────────────────────────
   Footer
   ────────────────────────────────────────────── */
.footer { border-top: 1px solid var(--border); padding: 1.5rem 0; }

.footer__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.footer__inner > p {
  font-size: 0.76rem;
  color: var(--muted);
}

.footer__links { display: flex; gap: 1.25rem; }

.footer__links a {
  font-size: 0.76rem;
  color: var(--muted);
  transition: color 0.15s;
}
.footer__links a:hover { color: var(--text); }

/* ──────────────────────────────────────────────
   Responsive
   ────────────────────────────────────────────── */
@media (max-width: 860px) {
  .grid { grid-template-columns: repeat(2, 1fr); }
  .research-row--single,
  .research-row--double,
  .research-row--articles { grid-template-columns: 1fr; }

  .hero__inner {
    grid-template-columns: 1fr;
    gap: 2rem;
    padding-block: 2.5rem;
  }

  .hero__contact {
    gap: 0.75rem;
  }

  .feature-card {
    flex-direction: column;
    align-items: flex-start;
    gap: 1.75rem;
    padding: 2rem;
  }
}

@media (max-width: 580px) {
  .header__inner {
    height: auto;
    padding-block: 0.75rem;
    flex-wrap: wrap;
    gap: 0.5rem;
  }

  .header__contact { display: none; }

  .tab-nav {
    order: 3;
    width: 100%;
  }

  .tab-btn {
    flex: 1;
    text-align: center;
    padding-inline: 0.5rem;
  }

  .logo-name { display: none; }

  .grid { grid-template-columns: 1fr; }

  .panel__header { flex-direction: column; gap: 0.3rem; }

  .footer__inner {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
  }
}