:root {
  --bg: #f3f7fb;
  --surface: #ffffff;
  --text: #0f172a;
  --muted: #4b5563;
  --border: #d6e1ed;
  --accent: #0f766e;
  --accent-soft: rgba(15, 118, 110, 0.12);
  --warning: #b45309;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Manrope", "Segoe UI", sans-serif;
  color: var(--text);
  background: var(--bg);
}

.container {
  width: min(1120px, 92vw);
  margin: 0 auto;
}

.header {
  padding: 1.5rem 0 0.8rem;
}

.back-link {
  color: var(--accent);
  text-decoration: none;
  font-weight: 700;
}

h1,
h2,
h3 {
  margin: 0;
}

h1 {
  margin-top: 0.6rem;
  font-size: clamp(1.8rem, 3.8vw, 2.7rem);
}

.header p {
  color: var(--muted);
  margin: 0.45rem 0 0;
}

.layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 1rem;
  padding-bottom: 2rem;
}

.panel {
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--surface);
  box-shadow: 0 18px 34px rgba(15, 23, 42, 0.08);
}

.controls {
  padding: 1rem;
}

.tabs {
  margin-top: 0.7rem;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.4rem;
}

.tab {
  border: 1px solid var(--border);
  background: #f4f8ff;
  border-radius: 10px;
  padding: 0.45rem;
  cursor: pointer;
  font: inherit;
}

.tab.active {
  background: var(--accent);
  border-color: transparent;
  color: #ffffff;
  font-weight: 700;
}

label {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  margin-top: 0.8rem;
  color: var(--muted);
}

input,
textarea,
button {
  font: inherit;
}

input,
textarea {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.5rem;
  background: #f9fbff;
  color: var(--text);
  font-family: "JetBrains Mono", monospace;
}

textarea {
  resize: vertical;
  min-height: 88px;
}

.button-grid {
  margin-top: 0.8rem;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.4rem;
}

button {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #eff5ff;
  color: var(--text);
  padding: 0.45rem 0.7rem;
  cursor: pointer;
}

button.primary {
  background: var(--accent);
  color: #ffffff;
  border-color: transparent;
}

button:hover {
  border-color: #9ab4d7;
}

.hidden {
  display: none;
}

.status {
  min-height: 1.25rem;
  margin-top: 0.75rem;
  color: var(--muted);
}

.shortcut-note {
  margin: 0.3rem 0 0;
  color: var(--muted);
  font-size: 0.84rem;
  line-height: 1.5;
}

#workspace-shelf-summary {
  margin-top: 0.35rem;
}

kbd {
  border: 1px solid rgba(148, 163, 184, 0.35);
  border-radius: 0.35rem;
  padding: 0.05rem 0.3rem;
  background: rgba(15, 23, 42, 0.08);
  font: inherit;
  font-family: "JetBrains Mono", monospace;
}

.mono {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.82rem;
}

.metric-card {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #f8fbff;
  padding: 0.35rem 0.45rem;
}

.metric-card h4 {
  margin: 0;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.metric-card p {
  margin: 0.2rem 0 0;
  font-family: "JetBrains Mono", monospace;
  color: var(--text);
}

.complexity-panel {
  margin-top: 0.85rem;
}

.complexity-panel h3 {
  margin: 0 0 0.65rem;
}

.log {
  list-style: none;
  margin: 0.5rem 0 0;
  padding: 0;
  max-height: 250px;
  overflow: auto;
  display: grid;
  gap: 0.35rem;
}

.log li {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.38rem 0.5rem;
  font-size: 0.85rem;
  color: var(--muted);
  background: #f8fbff;
}

.visual {
  padding: 1rem;
}

.visual-head p {
  margin: 0.35rem 0 0;
  color: var(--muted);
}

.snapshot-panel {
  margin-top: 1rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: linear-gradient(180deg, rgba(110, 168, 254, 0.08), rgba(255, 255, 255, 0.98));
}

.snapshot-panel h3 {
  margin: 0;
  font-size: 1rem;
}

.playbook-panel {
  margin-top: 0.85rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: linear-gradient(180deg, rgba(15, 118, 110, 0.08), rgba(255, 255, 255, 0.98));
}

.integrity-panel {
  margin-top: 0.85rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: linear-gradient(180deg, rgba(98, 70, 234, 0.08), rgba(255, 255, 255, 0.98));
}

.invariant-list {
  margin: 0.55rem 0 0;
  padding-left: 1.1rem;
  color: var(--muted);
  display: grid;
  gap: 0.25rem;
}

.playbook-panel h3 {
  margin: 0;
  font-size: 1rem;
}

.playbook-title {
  margin: 0.55rem 0 0;
  font-weight: 700;
  color: var(--text);
}

.playbook-watch {
  margin: 0.55rem 0 0;
  color: var(--muted);
  font-size: 0.86rem;
}

.snapshot-chips {
  margin-top: 0.75rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.snapshot-chip {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.4rem 0.7rem;
  background: #ffffff;
  font-size: 0.83rem;
  color: var(--muted);
}

.visual-area {
  margin-top: 0.8rem;
  min-height: 430px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fbfdff;
  padding: 0.9rem;
}

.analysis-disclosure {
  margin-top: 0.85rem;
}

.analysis-disclosure summary {
  cursor: pointer;
  color: var(--accent);
  font-weight: 700;
}

.analysis-disclosure[open] summary {
  margin-bottom: 0.8rem;
}

.node-list {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
  align-items: center;
  min-height: 100%;
}

.stack-list {
  flex-direction: column;
  justify-content: flex-end;
  align-items: flex-start;
}

.node {
  border: 2px solid var(--accent);
  border-radius: 10px;
  background: #ecfdf5;
  color: var(--text);
  padding: 0.55rem 0.75rem;
  font-family: "JetBrains Mono", monospace;
  min-width: 80px;
  text-align: center;
  box-shadow: 0 8px 16px rgba(15, 118, 110, 0.12);
}

.node.active {
  background: #fef3c7;
  border-color: #d97706;
}

.node.found {
  background: #bbf7d0;
  border-color: #15803d;
}

.node.badge::after {
  display: block;
  margin-top: 0.25rem;
  color: var(--warning);
  font-size: 0.72rem;
  font-family: "Manrope", sans-serif;
  text-transform: uppercase;
}

.node.top::after { content: 'top'; }
.node.front::after { content: 'front'; }
.node.head::after { content: 'root'; }
.node.list-head::after { content: 'head'; }

.empty {
  color: var(--muted);
  font-style: italic;
}

.demo-strip {
  margin-top: 1rem;
  border: 1px solid rgba(20, 184, 166, 0.32);
  border-radius: 10px;
  background: rgba(20, 184, 166, 0.08);
  padding: 0.8rem 1rem;
  color: var(--muted);
}

.demo-strip strong {
  color: var(--text);
}

.tree-svg {
  width: 100%;
  height: 100%;
}

.tree-line {
  stroke: #93a7c3;
  stroke-width: 2;
}

.tree-node circle {
  fill: #ecfdf5;
  stroke: var(--accent);
  stroke-width: 2;
}

.tree-node text {
  font-family: "JetBrains Mono", monospace;
  fill: var(--text);
  text-anchor: middle;
  dominant-baseline: middle;
  font-size: 12px;
}

.tree-node.active circle {
  fill: #fef3c7;
  stroke: #b45309;
}

.tree-node.found circle {
  fill: #86efac;
  stroke: #166534;
}

@media (max-width: 980px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .visual-area {
    min-height: 340px;
  }
}