:root {
  --bg: #0e0e0f;
  --bg2: #161618;
  --bg3: #1e1e21;
  --border: rgba(255,255,255,0.08);
  --border2: rgba(255,255,255,0.14);
  --text: #e8e6df;
  --text2: #9b9891;
  --text3: #5e5c58;
  --green: #5de4a0;
  --green2: #2a7a52;
  --green-dim: rgba(93,228,160,0.1);
  --blue: #5db8ff;
  --blue-dim: rgba(93,184,255,0.1);
  --amber: #f5c542;
  --amber-dim: rgba(245,197,66,0.1);
  --coral: #ff7b6b;
  --coral-dim: rgba(255,123,107,0.1);
  --purple: #b98bff;
  --purple-dim: rgba(185,139,255,0.1);
  --code-bg: #0a0a0b;
  --panel-soft: rgba(255,255,255,0.02);
  --mono: 'JetBrains Mono', monospace;
  --serif: 'Gowun Batang', serif;
  --sans: 'Noto Sans KR', sans-serif;
}

body[data-theme="light"] {
  --bg: #f5f2ea;
  --bg2: #fbf9f3;
  --bg3: #f0ece2;
  --border: rgba(24, 22, 18, 0.08);
  --border2: rgba(24, 22, 18, 0.14);
  --text: #181612;
  --text2: #5f5a51;
  --text3: #8a8478;
  --green: #1f8b57;
  --green2: rgba(31, 139, 87, 0.35);
  --green-dim: rgba(31, 139, 87, 0.08);
  --blue: #266db3;
  --blue-dim: rgba(38, 109, 179, 0.08);
  --amber: #b57b00;
  --amber-dim: rgba(181, 123, 0, 0.09);
  --coral: #c65a4d;
  --coral-dim: rgba(198, 90, 77, 0.08);
  --purple: #7757c8;
  --purple-dim: rgba(119, 87, 200, 0.08);
  --code-bg: #ece7dd;
  --panel-soft: rgba(24, 22, 18, 0.025);
}

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

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-weight: 300;
  line-height: 1.8;
  min-height: 100vh;
}

a { color: inherit; }

nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(14,14,15,0.9);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  padding: 0 2rem;
  display: flex;
  align-items: center;
  gap: 0;
  height: 52px;
}

.nav-logo {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--green);
  letter-spacing: .12em;
  margin-right: 2rem;
  white-space: nowrap;
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 0;
  flex: 1;
  overflow-x: auto;
  scrollbar-width: none;
}

.nav-links::-webkit-scrollbar { display: none; }

.nav-link {
  font-size: 12px;
  color: var(--text3);
  padding: 0 14px;
  height: 52px;
  display: flex;
  align-items: center;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  transition: all .2s;
  cursor: pointer;
  text-decoration: none;
  font-weight: 400;
  letter-spacing: .02em;
}

.nav-link:hover { color: var(--text2); }
.nav-link.active { color: var(--green); border-bottom-color: var(--green); }

.nav-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-left: 1rem;
}

.theme-toggle {
  min-width: 82px;
  height: 32px;
  padding: 0 12px;
  border-radius: 999px;
  border: 1px solid var(--border2);
  background: var(--bg2);
  color: var(--text2);
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .04em;
  cursor: pointer;
  transition: all .2s ease;
}

.theme-toggle:hover {
  color: var(--text);
  border-color: var(--green2);
}

main { max-width: 860px; margin: 0 auto; padding: 80px 2rem 4rem; }

.hero { padding: 4rem 0 3rem; border-bottom: 1px solid var(--border); margin-bottom: 3rem; }
.hero-tag { font-family: var(--mono); font-size: 11px; color: var(--green); letter-spacing: .16em; margin-bottom: 1rem; }
.hero-title { font-family: var(--serif); font-size: clamp(2rem,5vw,3.2rem); font-weight: 700; line-height: 1.2; margin-bottom: 1rem; }
.hero-title span { color: var(--green); }
.hero-sub { font-size: 15px; color: var(--text2); max-width: 560px; }

.section { margin-bottom: 5rem; scroll-margin-top: 70px; }
.section-header { display: flex; align-items: center; gap: 12px; margin-bottom: 1.5rem; }
.section-num { font-family: var(--mono); font-size: 11px; color: var(--green); border: 1px solid var(--green2); padding: 2px 8px; border-radius: 3px; }
.section-title { font-family: var(--serif); font-size: 1.5rem; font-weight: 700; }

p { font-size: 14.5px; color: var(--text2); margin-bottom: 1rem; }
p strong { color: var(--text); font-weight: 500; }
.keyword { color: var(--green); font-weight: 500; font-family: var(--mono); font-size: .9em; }

.card { background: var(--bg2); border: 1px solid var(--border); border-radius: 10px; padding: 1.25rem 1.5rem; margin-bottom: 1rem; }
.card-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-bottom: 1.5rem; }
.card-grid.with-top-gap { margin-top: 1.25rem; }
.card-head { font-size: 11px; letter-spacing: .1em; font-family: var(--mono); margin-bottom: 8px; }
.card-desc { font-size: 13px; color: var(--text2); line-height: 1.7; }
.card.green { border-color: var(--green2); background: var(--green-dim); }
.card.blue { border-color: rgba(93,184,255,0.25); background: var(--blue-dim); }
.card.amber { border-color: rgba(245,197,66,0.25); background: var(--amber-dim); }
.card.coral { border-color: rgba(255,123,107,0.25); background: var(--coral-dim); }

.code-block {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.9;
  white-space: pre-wrap;
  overflow-x: auto;
  margin: 1.25rem 0;
}

.code-block.with-top-gap { margin-top: 1.5rem; }
.code-label { font-size: 10px; color: var(--text3); letter-spacing: .1em; margin-bottom: 8px; font-family: var(--mono); display: block; }
.ck { color: #ff7b6b; }
.ct { color: #5db8ff; }
.cm { color: #9b9891; font-style: italic; }
.cs { color: #5de4a0; }
.cf { color: #b98bff; }
.co { color: #f5c542; }

.tree-wrap { background: var(--bg2); border: 1px solid var(--border); border-radius: 10px; padding: 1.5rem; margin: 1.25rem 0; overflow-x: auto; }
.tree-wrap.with-top-gap { margin-top: 1.5rem; }
.tree-label { font-family: var(--mono); font-size: 11px; color: var(--text3); margin-bottom: 12px; letter-spacing: .08em; }

.highlight-box {
  border-left: 3px solid var(--green);
  background: var(--green-dim);
  border-radius: 0 8px 8px 0;
  padding: 1rem 1.25rem;
  margin: 1.25rem 0;
  font-size: 14px;
  color: var(--text);
  line-height: 1.8;
}

.highlight-box.blue { border-left-color: var(--blue); background: var(--blue-dim); }
.highlight-box.amber { border-left-color: var(--amber); background: var(--amber-dim); }

.table-wrap { overflow-x: auto; margin: 1.25rem 0; }
.table-wrap.with-top-gap { margin-top: 2rem; }
table { width: 100%; border-collapse: collapse; font-size: 13px; }
th { text-align: left; padding: 9px 14px; font-family: var(--mono); font-size: 11px; letter-spacing: .08em; color: var(--text3); border-bottom: 1px solid var(--border2); font-weight: 400; }
td { padding: 10px 14px; border-bottom: 1px solid var(--border); color: var(--text2); }
td:first-child { color: var(--text); font-weight: 500; }
td code { font-family: var(--mono); font-size: 12px; color: var(--green); }
.good { color: var(--green) !important; }
.bad { color: var(--coral) !important; }

.step-ctrl { display: flex; gap: 8px; align-items: center; margin: 12px 0; flex-wrap: wrap; }
.btn {
  font-family: var(--sans);
  font-size: 12px;
  padding: 6px 16px;
  border: 1px solid var(--border2);
  border-radius: 5px;
  background: transparent;
  color: var(--text2);
  cursor: pointer;
  transition: all .15s;
  font-weight: 400;
}

.btn:hover:not(:disabled) { border-color: var(--green); color: var(--green); }
.btn:disabled { opacity: .35; cursor: default; }
.btn.primary { border-color: var(--green2); color: var(--green); }
.badge { font-family: var(--mono); font-size: 11px; padding: 3px 10px; border-radius: 3px; background: var(--green-dim); color: var(--green); border: 1px solid var(--green2); }
.step-log { font-size: 13px; color: var(--text2); padding: 10px 14px; background: var(--bg3); border-radius: 6px; margin-top: 8px; border-left: 2px solid var(--green2); line-height: 1.7; }

.progress-steps { display: flex; gap: 6px; margin-bottom: 14px; flex-wrap: wrap; }
.ps { font-size: 11px; padding: 4px 12px; border-radius: 3px; border: 1px solid var(--border); color: var(--text3); font-family: var(--mono); transition: all .2s; }
.ps.active { border-color: var(--green2); color: var(--green); background: var(--green-dim); }
.ps.done { border-color: var(--border2); color: var(--text3); }

.formula { font-family: var(--mono); font-size: 13px; background: var(--code-bg); border: 1px solid var(--border); border-radius: 6px; padding: 10px 16px; color: var(--green); display: inline-block; margin: 4px 0; }

.array-row { display: flex; gap: 4px; flex-wrap: wrap; margin: 10px 0; }
.arr-cell { display: flex; flex-direction: column; align-items: center; gap: 3px; }
.arr-idx { font-family: var(--mono); font-size: 10px; color: var(--text3); }
.arr-val { width: 40px; height: 40px; display: flex; align-items: center; justify-content: center; font-family: var(--mono); font-size: 13px; font-weight: 600; border: 1px solid var(--border2); border-radius: 5px; background: var(--bg3); color: var(--text); transition: all .3s; }
.arr-val.hi-green { background: var(--green-dim); border-color: var(--green2); color: var(--green); }
.arr-val.hi-blue { background: var(--blue-dim); border-color: rgba(93,184,255,0.4); color: var(--blue); }
.arr-val.hi-amber { background: var(--amber-dim); border-color: rgba(245,197,66,0.4); color: var(--amber); }
.arr-val.hi-coral { background: var(--coral-dim); border-color: rgba(255,123,107,0.4); color: var(--coral); }

.divider { border: none; border-top: 1px solid var(--border); margin: 3rem 0; }

.text-green { color: var(--green); }
.text-blue { color: var(--blue); }
.text-amber { color: var(--amber); }
.text-coral { color: var(--coral); }
.text-purple { color: var(--purple); }
.text-main { color: var(--text); }
.text-subtle { color: var(--text2); }
.font-mono { font-family: var(--mono); }
.font-sans { font-family: var(--sans); }

.mt-half { margin-top: 0.5rem; }
.mt-md { margin-top: 1.25rem; }
.mt-lg { margin-top: 1.5rem; }
.mt-xl { margin-top: 2rem; }

.legend-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 10px; font-size: 11px; font-family: var(--mono); }
.formula-row { margin-top: 10px; display: flex; flex-wrap: wrap; gap: 16px; }
.section-intro { margin: 1.5rem 0 0.5rem; }
.section-intro.tight { margin: 2rem 0 0.5rem; }
.section-kicker { font-family: var(--mono); font-size: 12px; letter-spacing: .1em; }
.section-kicker.green { color: var(--green); }
.section-kicker.coral { color: var(--coral); }
.section-copy { margin-top: 8px; }
.array-panel-head { margin-top: 14px; }
.array-panel-label { font-family: var(--mono); font-size: 11px; color: var(--text3); margin-bottom: 8px; letter-spacing: .08em; }
.problem-head { line-height: 1.9; }
.svg-block { display: block; max-width: 620px; font-family: 'Noto Sans KR', sans-serif; }
.svg-block.clickable { cursor: pointer; }

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 1.5rem;
}

.pill-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 38px;
  padding: 0 14px;
  border-radius: 999px;
  border: 1px solid var(--border2);
  text-decoration: none;
  font-size: 12px;
  color: var(--text2);
  transition: all .2s;
}

.pill-link:hover {
  color: var(--text);
  border-color: var(--green2);
}

.pill-link.primary {
  color: var(--green);
  border-color: var(--green2);
  background: var(--green-dim);
}

.overview-grid {
  display: grid;
  grid-template-columns: 1.3fr .9fr;
  gap: 12px;
  margin-bottom: 1.5rem;
}

.stack-list {
  display: grid;
  gap: 12px;
}

.topic-card {
  display: block;
  text-decoration: none;
  transition: transform .18s ease, border-color .18s ease, background .18s ease;
}

.topic-card:hover {
  transform: translateY(-2px);
  border-color: var(--green2);
}

.topic-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
}

.topic-title {
  font-family: var(--serif);
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 10px;
}

.topic-desc {
  font-size: 13px;
  color: var(--text2);
  line-height: 1.8;
}

.topic-foot {
  margin-top: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  font-size: 12px;
  color: var(--text3);
}

.topic-arrow {
  color: var(--green);
  font-family: var(--mono);
}

.status-chip {
  display: inline-flex;
  align-items: center;
  min-height: 24px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid var(--border2);
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: .08em;
  color: var(--text3);
}

.status-chip.ready {
  color: var(--green);
  border-color: var(--green2);
  background: var(--green-dim);
}

.status-chip.soon {
  color: var(--amber);
  border-color: rgba(245,197,66,0.25);
  background: var(--amber-dim);
}

.mini-list {
  display: grid;
  gap: 10px;
}

.mini-item {
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel-soft);
}

.mini-kicker {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: .08em;
  color: var(--text3);
  margin-bottom: 4px;
}

.mini-title {
  font-size: 13px;
  color: var(--text);
  margin-bottom: 2px;
}

.mini-copy {
  font-size: 12px;
  color: var(--text2);
}

.roadmap-table td:last-child {
  color: var(--text2);
}

.mono-note {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text2);
}

.matrix-wrap {
  overflow-x: auto;
  margin: 1rem 0;
}

.matrix-table {
  width: auto;
  min-width: 320px;
}

.matrix-table th,
.matrix-table td {
  text-align: center;
  min-width: 52px;
}

.matrix-table td.active {
  color: var(--green);
  background: var(--green-dim);
}

.matrix-table td.skip {
  color: var(--text3);
}

.adj-list {
  display: grid;
  gap: 8px;
  margin-top: 1rem;
}

.adj-row {
  display: flex;
  gap: 10px;
  align-items: center;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg3);
  font-size: 13px;
}

.adj-node {
  min-width: 54px;
  font-family: var(--mono);
  color: var(--green);
}

.adj-values {
  color: var(--text2);
  font-family: var(--mono);
}

.sim-grid {
  display: grid;
  grid-template-columns: 1.1fr .9fr;
  gap: 12px;
  align-items: start;
}

.stack-panel {
  display: grid;
  gap: 12px;
}

.state-box {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg3);
  padding: 12px 14px;
}

.state-label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
  color: var(--text3);
  margin-bottom: 8px;
}

.queue-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.queue-chip {
  min-width: 34px;
  height: 30px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid var(--border2);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text);
  background: var(--bg2);
}

.queue-chip.active {
  color: var(--green);
  border-color: var(--green2);
  background: var(--green-dim);
}

.state-inline {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.visited-chip {
  min-width: 44px;
  height: 30px;
  padding: 0 10px;
  border-radius: 8px;
  border: 1px solid var(--border2);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text3);
  background: var(--bg2);
}

.visited-chip.on {
  color: var(--green);
  border-color: var(--green2);
  background: var(--green-dim);
}

.network-chip {
  min-width: 68px;
  height: 32px;
  padding: 0 12px;
  border-radius: 999px;
  border: 1px solid var(--border2);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text2);
  background: var(--bg2);
}

.network-chip.on {
  color: var(--amber);
  border-color: rgba(245,197,66,0.25);
  background: var(--amber-dim);
}

.diagram-svg {
  display: block;
  width: 100%;
  max-width: 620px;
  font-family: 'Noto Sans KR', sans-serif;
}

.site-footer {
  margin-top: 4rem;
  padding: 1.5rem 0 0;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

.footer-copy {
  font-size: 12px;
  color: var(--text3);
}

.footer-link {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
  color: var(--green);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color .2s ease, color .2s ease;
}

.footer-link:hover {
  color: var(--text);
  border-color: var(--green2);
}

@media (max-width: 600px) {
  .card-grid { grid-template-columns: 1fr; }
}

@media (max-width: 760px) {
  .overview-grid { grid-template-columns: 1fr; }
  .sim-grid { grid-template-columns: 1fr; }
  nav { padding: 0 1rem; }
  .nav-actions { margin-left: .5rem; }
  .theme-toggle { min-width: 70px; padding: 0 10px; }
}