feat: 3D renderer of plantuml diagram

Adds initial conversation with Claude along with the .html diagram
renderer.

conversation-summary.md

@@ -0,0 +1,118 @@
+# Conversation summary — PlantUML isometric 3D renderer
+
+## Context
+
+This conversation explored generating interactive 3D/isometric renderings of embedded system architecture diagrams, with a specific focus on an automotive ECU use case. The team uses PlantUML and self-hosts the PlantUML server.
+
+---
+
+## System being modelled
+
+Three top-level ECUs: **A**, **B**, and **C**.
+
+**ECU B** contains:
+- A **Connector** and an **Adapter** for each of ECU A and ECU C (two parallel lanes)
+- Both adapters feed into a single **Logic** component
+- Inside Logic, a sequential sub-flow: **a → b → c**
+
+PlantUML source:
+
+```plantuml
+@startuml
+component "ECU A" as A
+component "ECU C" as C
+
+component "ECU B" as B {
+  component "Connector A" as ConA
+  component "Adapter A" as AdpA
+  component "Connector C" as ConC
+  component "Adapter C" as AdpC
+  component "Logic" as L {
+    component "a" as La
+    component "b" as Lb
+    component "c" as Lc
+    La --> Lb
+    Lb --> Lc
+  }
+  ConA --> AdpA
+  ConC --> AdpC
+  AdpA --> L
+  AdpC --> L
+}
+
+A --> ConA
+C --> ConC
+@enduml
+```
+
+---
+
+## What was built
+
+An interactive isometric 3D renderer that:
+
+1. **Parses PlantUML component diagram syntax** client-side (no server required for the parser itself)
+2. **Renders an isometric SVG** — each component is a 3-faced isometric block with color coding by component type
+3. **Supports drill-down zoom** — clicking a component with nested children transitions to an internal view, with a breadcrumb trail for navigation
+4. **Color scheme by component type:**
+   - Gray → ECU / top-level components
+   - Teal → Connectors
+   - Amber → Adapters
+   - Purple → Logic components
+   - Coral → Sequence steps (short labels like a, b, c)
+
+A standalone `plantuml-3d-renderer.html` file was produced — open it directly in any browser or VSCode Live Preview.
+
+---
+
+## Architecture decisions
+
+### Parser approach
+The client-side parser handles:
+- `component "Label" as alias { ... }` — with or without braces
+- `component alias { ... }` — unlabelled alias form
+- `alias --> alias : optional label` — directed connections
+- Arbitrary nesting depth
+
+**For production:** POST the `.puml` source to your self-hosted PlantUML server's `/json` endpoint and drive the renderer from the returned AST instead. This handles edge cases (stereotypes, notes, skinparam, grouped interfaces) that the lightweight client-side parser skips.
+
+### Rendering
+- Pure SVG, no dependencies
+- Isometric projection: each block has top/left/right faces using CSS custom properties for colors
+- Dark mode automatic via `prefers-color-scheme`
+- Zoom levels are discrete view transitions (not CSS transforms) — each level is a full redraw of the SVG for the selected node's children
+
+---
+
+## DSL alternatives considered
+
+| Tool | License | Notes |
+|---|---|---|
+| **PlantUML** | GPL / LGPL (jar) | Team already uses it. Self-hosting fine for commercial internal use. Get a free Professional Edition key to suppress ads. |
+| **Mermaid** | MIT | Simplest license, no restrictions. Less expressive for deep nesting. |
+| **D2** | MPL 2.0 | Clean syntax, good nesting. TALA layout engine requires paid license for commercial use. |
+| **Structurizr DSL** | Apache 2.0 | C4-model based. Server prebuilt binaries need a license; build from source is free. |
+| **ArchiMate** | Non-commercial free / annual commercial license | The Archi tool (MIT), but the language spec requires a commercial license from The Open Group for commercial use. |
+| **SysML** | Open source (OMG derived) | Semantically correct for ECU/embedded systems. Heavy tooling (Cameo, Papyrus). Eclipse SysON is open source. |
+| **AADL** | SAE standard (spec costs money; OSATE tooling is open source) | Best fit for automotive embedded. Steep learning curve. |
+
+**Recommendation:** Stay on PlantUML. The team's existing knowledge compounds in value faster than any migration would justify — unless moving toward full MBSE (model-based systems engineering) with SysML or AADL.
+
+---
+
+## Next steps / open threads
+
+- [ ] Wire the renderer to the self-hosted PlantUML `/json` endpoint instead of the client-side parser
+- [ ] Add animated connection flows (data flowing between components)
+- [ ] Support PlantUML stereotypes (`<<ECU>>`, `<<connector>>`) as an explicit color override mechanism, removing the label-inference heuristic
+- [ ] Consider a VSCode extension wrapper: watch `.puml` files, re-render on save, show isometric view in a side panel
+- [ ] Explore Three.js for true 3D with orbit/zoom controls, for stakeholder presentation use cases
+
+---
+
+## How to continue in VSCode
+
+1. Open `plantuml-3d-renderer.html` with Live Preview or any browser
+2. Start a new Claude chat (Claude Code CLI or Copilot+Claude) and paste this summary
+3. The renderer source is self-contained — all logic is in the single HTML file
+4. Key function to extend: `parsePuml(src)` for parser changes, `drawLevel(node)` for rendering changes, `guessColor(node)` for color mapping changes

plantuml-3d-renderer.html

@@ -0,0 +1,594 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="UTF-8">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>PlantUML → Isometric 3D Renderer</title>
+<style>
+  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
+
+  :root {
+    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+    --font-mono: "JetBrains Mono", "Fira Code", "Cascadia Code", monospace;
+    --bg:        #ffffff;
+    --bg2:       #f5f4f0;
+    --bg3:       #eeecea;
+    --txt:       #1a1a1a;
+    --txts:      #555550;
+    --txt3:      #888780;
+    --border:    rgba(0,0,0,0.12);
+    --border2:   rgba(0,0,0,0.22);
+    --info-bg:   #e6f1fb;
+    --info-txt:  #0c447c;
+    --info-bdr:  #378add;
+    --sk:        rgba(0,0,0,0.13);
+    --top-gray:  #D3D1C7; --left-gray:  #888780; --right-gray:  #5F5E5A;
+    --top-blue:  #B5D4F4; --left-blue:  #378ADD; --right-blue:  #185FA5;
+    --top-teal:  #9FE1CB; --left-teal:  #1D9E75; --right-teal:  #0F6E56;
+    --top-amber: #FAC775; --left-amber: #BA7517; --right-amber: #854F0B;
+    --top-purple:#CECBF6; --left-purple:#7F77DD; --right-purple:#534AB7;
+    --top-coral: #F5C4B3; --left-coral: #D85A30; --right-coral: #993C1D;
+    --radius:    8px;
+  }
+
+  @media (prefers-color-scheme: dark) {
+    :root {
+      --bg:        #1e1e1e;
+      --bg2:       #2a2a2a;
+      --bg3:       #333333;
+      --txt:       #e8e6dc;
+      --txts:      #9c9a92;
+      --txt3:      #666660;
+      --border:    rgba(255,255,255,0.1);
+      --border2:   rgba(255,255,255,0.2);
+      --info-bg:   #042c53;
+      --info-txt:  #85b7eb;
+      --info-bdr:  #185fa5;
+      --sk:        rgba(255,255,255,0.08);
+      --top-gray:  #2C2C2A; --left-gray:  #444441; --right-gray:  #1a1a18;
+      --top-blue:  #0C447C; --left-blue:  #185FA5; --right-blue:  #042C53;
+      --top-teal:  #085041; --left-teal:  #0F6E56; --right-teal:  #04342C;
+      --top-amber: #633806; --left-amber: #854F0B; --right-amber: #412402;
+      --top-purple:#3C3489; --left-purple:#534AB7; --right-purple:#26215C;
+      --top-coral: #712B13; --left-coral: #993C1D; --right-coral: #4A1B0C;
+    }
+  }
+
+  body {
+    font-family: var(--font-sans);
+    background: var(--bg);
+    color: var(--txt);
+    padding: 24px;
+    min-height: 100vh;
+  }
+
+  h1 {
+    font-size: 18px;
+    font-weight: 500;
+    margin-bottom: 4px;
+  }
+
+  .subtitle {
+    font-size: 13px;
+    color: var(--txts);
+    margin-bottom: 20px;
+  }
+
+  .layout {
+    display: grid;
+    grid-template-columns: 320px 1fr;
+    gap: 20px;
+    align-items: start;
+  }
+
+  @media (max-width: 700px) {
+    .layout { grid-template-columns: 1fr; }
+  }
+
+  .panel {
+    background: var(--bg2);
+    border: 0.5px solid var(--border2);
+    border-radius: var(--radius);
+    padding: 16px;
+  }
+
+  .panel-label {
+    font-size: 11px;
+    font-weight: 500;
+    color: var(--txt3);
+    text-transform: uppercase;
+    letter-spacing: 0.06em;
+    margin-bottom: 10px;
+  }
+
+  textarea {
+    width: 100%;
+    height: 320px;
+    font-family: var(--font-mono);
+    font-size: 12px;
+    line-height: 1.6;
+    padding: 10px;
+    resize: vertical;
+    background: var(--bg);
+    color: var(--txt);
+    border: 0.5px solid var(--border2);
+    border-radius: var(--radius);
+    outline: none;
+  }
+
+  textarea:focus { border-color: var(--info-bdr); }
+
+  .btn-row {
+    display: flex;
+    gap: 8px;
+    margin-top: 10px;
+    align-items: center;
+  }
+
+  button {
+    font-family: var(--font-sans);
+    font-size: 13px;
+    padding: 7px 16px;
+    border-radius: var(--radius);
+    border: 0.5px solid var(--border2);
+    background: transparent;
+    color: var(--txt);
+    cursor: pointer;
+  }
+
+  button:hover { background: var(--bg3); }
+  button:active { transform: scale(0.98); }
+
+  button.primary {
+    background: var(--info-bg);
+    color: var(--info-txt);
+    border-color: var(--info-bdr);
+    font-weight: 500;
+  }
+
+  #err {
+    font-size: 12px;
+    color: #c0392b;
+    margin-top: 6px;
+    min-height: 16px;
+  }
+
+  .legend {
+    margin-top: 14px;
+    display: flex;
+    flex-wrap: wrap;
+    gap: 8px;
+  }
+
+  .legend-item {
+    display: flex;
+    align-items: center;
+    gap: 5px;
+    font-size: 11px;
+    color: var(--txts);
+  }
+
+  .legend-swatch {
+    width: 12px;
+    height: 12px;
+    border-radius: 2px;
+    border: 0.5px solid var(--border);
+  }
+
+  .hint-box {
+    margin-top: 12px;
+    padding: 8px 10px;
+    background: var(--info-bg);
+    border: 0.5px solid var(--info-bdr);
+    border-radius: var(--radius);
+    font-size: 11px;
+    color: var(--info-txt);
+    line-height: 1.5;
+  }
+
+  .canvas-panel {
+    background: var(--bg2);
+    border: 0.5px solid var(--border2);
+    border-radius: var(--radius);
+    overflow: hidden;
+  }
+
+  .canvas-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    padding: 10px 14px;
+    border-bottom: 0.5px solid var(--border);
+  }
+
+  #nav {
+    font-size: 12px;
+    color: var(--txts);
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    flex-wrap: wrap;
+  }
+
+  #nav .crumb {
+    cursor: pointer;
+    text-decoration: underline;
+    text-underline-offset: 2px;
+    color: var(--info-txt);
+  }
+
+  #nav .crumb:hover { opacity: 0.75; }
+  #nav .sep { opacity: 0.35; }
+
+  #canvas-wrap {
+    padding: 8px;
+    background: var(--bg);
+  }
+
+  svg { display: block; }
+
+  .iso-lbl {
+    font-family: var(--font-sans);
+    font-size: 11px;
+    fill: var(--txt, #1a1a1a);
+  }
+
+  .iso-sub {
+    font-family: var(--font-sans);
+    font-size: 9px;
+    fill: var(--txts, #555);
+  }
+
+  .zoomable { cursor: zoom-in; }
+  .zoomable:hover polygon:first-child { opacity: 0.82; }
+  .conn   { stroke-width: 1;   fill: none; stroke-dasharray: 4 3; }
+  .conn-s { stroke-width: 1.5; fill: none; }
+</style>
+</head>
+<body>
+
+<h1>PlantUML → Isometric 3D Renderer</h1>
+<p class="subtitle">Paste a PlantUML component diagram and click Render to generate an interactive isometric view.</p>
+
+<div class="layout">
+  <div class="panel">
+    <div class="panel-label">PlantUML source</div>
+    <textarea id="puml" spellcheck="false">@startuml
+component "ECU A" as A
+component "ECU C" as C
+
+component "ECU B" as B {
+  component "Connector A" as ConA
+  component "Adapter A" as AdpA
+  component "Connector C" as ConC
+  component "Adapter C" as AdpC
+  component "Logic" as L {
+    component "a" as La
+    component "b" as Lb
+    component "c" as Lc
+    La --> Lb
+    Lb --> Lc
+  }
+  ConA --> AdpA
+  ConC --> AdpC
+  AdpA --> L
+  AdpC --> L
+}
+
+A --> ConA
+C --> ConC
+@enduml</textarea>
+
+    <div class="btn-row">
+      <button class="primary" onclick="render()">Render →</button>
+      <button onclick="resetSource()">Reset example</button>
+    </div>
+    <div id="err"></div>
+
+    <div class="legend">
+      <div class="legend-item">
+        <div class="legend-swatch" style="background:var(--top-gray)"></div> ECU / top-level
+      </div>
+      <div class="legend-item">
+        <div class="legend-swatch" style="background:var(--top-teal)"></div> Connector
+      </div>
+      <div class="legend-item">
+        <div class="legend-swatch" style="background:var(--top-amber)"></div> Adapter
+      </div>
+      <div class="legend-item">
+        <div class="legend-swatch" style="background:var(--top-purple)"></div> Logic
+      </div>
+      <div class="legend-item">
+        <div class="legend-swatch" style="background:var(--top-coral)"></div> Sequence step
+      </div>
+    </div>
+
+    <div class="hint-box">
+      Color is inferred from the component label.<br>
+      Components with children are clickable — drill in to explore nested structure.
+      <br><br>
+      To connect your self-hosted PlantUML server, POST the source to
+      <code>/json</code> and feed the response AST into the renderer instead of the client-side parser.
+    </div>
+  </div>
+
+  <div class="canvas-panel">
+    <div class="canvas-header">
+      <div id="nav"><span style="color:var(--txt3)">Overview</span></div>
+    </div>
+    <div id="canvas-wrap">
+      <svg id="iso" width="100%" viewBox="0 0 680 400"></svg>
+    </div>
+  </div>
+</div>
+
+<script>
+const EXAMPLE = document.getElementById('puml').value;
+
+const PALETTE = {
+  ecu:   { t:'--top-gray',   l:'--left-gray',   r:'--right-gray'   },
+  conn:  { t:'--top-teal',   l:'--left-teal',   r:'--right-teal'   },
+  adp:   { t:'--top-amber',  l:'--left-amber',  r:'--right-amber'  },
+  logic: { t:'--top-purple', l:'--left-purple',  r:'--right-purple' },
+  seq:   { t:'--top-coral',  l:'--left-coral',  r:'--right-coral'  },
+};
+
+function cv(v) {
+  return getComputedStyle(document.documentElement).getPropertyValue(v).trim() || v;
+}
+
+function parsePuml(src) {
+  const lines = src.split('\n')
+    .map(s => s.trim())
+    .filter(s => s && !s.startsWith("'") && s !== '@startuml' && s !== '@enduml');
+
+  const root = { id: '__root__', label: 'root', children: [], conns: [] };
+  const stack = [root];
+  const byId = {};
+
+  const aliasRe       = /^component\s+"([^"]+)"\s+as\s+(\w+)\s*(\{)?\s*$/;
+  const aliasNoLblRe  = /^component\s+(\w+)\s*(\{)?\s*$/;
+  const connRe        = /^(\w+)\s*-->\s*(\w+)(?:\s*:\s*(.*))?$/;
+  const closeRe       = /^\}$/;
+
+  function cur() { return stack[stack.length - 1]; }
+
+  for (const line of lines) {
+    let m;
+    if ((m = aliasRe.exec(line))) {
+      const node = { id: m[2], label: m[1], children: [], conns: [], parent: cur() };
+      byId[m[2]] = node;
+      cur().children.push(node);
+      if (m[3]) stack.push(node);
+    } else if ((m = aliasNoLblRe.exec(line))) {
+      const node = { id: m[1], label: m[1], children: [], conns: [], parent: cur() };
+      byId[m[1]] = node;
+      cur().children.push(node);
+      if (m[2]) stack.push(node);
+    } else if ((m = connRe.exec(line))) {
+      cur().conns.push({ from: m[1], to: m[2], label: m[3] || '' });
+    } else if (closeRe.test(line)) {
+      if (stack.length > 1) stack.pop();
+    }
+  }
+  return { root, byId };
+}
+
+function guessColor(node) {
+  const l = node.label.toLowerCase();
+  if (l.startsWith('connector')) return PALETTE.conn;
+  if (l.startsWith('adapter'))   return PALETTE.adp;
+  if (l === 'logic' || l === 'logic component') return PALETTE.logic;
+  if (node.label.length <= 2)    return PALETTE.seq;
+  return PALETTE.ecu;
+}
+
+function ns(tag) {
+  return document.createElementNS('http://www.w3.org/2000/svg', tag);
+}
+
+function makePoly(pts, cssVar) {
+  const el = ns('polygon');
+  el.setAttribute('points', pts.map(p => p.join(',')).join(' '));
+  el.style.fill   = `var(${cssVar})`;
+  el.style.stroke = 'var(--sk)';
+  el.setAttribute('stroke-width', '0.5');
+  return el;
+}
+
+function makeBlock(svg, x, y, W, H, pal, label, sublabel, clickable) {
+  const g = ns('g');
+  if (clickable) g.classList.add('zoomable');
+
+  const hw = W, hh = W * 0.47;
+  const top   = makePoly([[x,y],[x+hw,y+hh],[x,y+hh*2],[x-hw,y+hh]], pal.t);
+  const left  = makePoly([[x-hw,y+hh],[x,y+hh*2],[x,y+hh*2+H],[x-hw,y+hh+H]], pal.l);
+  const right = makePoly([[x,y+hh*2],[x+hw,y+hh],[x+hw,y+hh+H],[x,y+hh*2+H]], pal.r);
+  g.appendChild(top); g.appendChild(left); g.appendChild(right);
+
+  const tx = ns('text');
+  tx.setAttribute('x', x); tx.setAttribute('y', y + hh + 2);
+  tx.setAttribute('text-anchor', 'middle');
+  tx.setAttribute('dominant-baseline', 'central');
+  tx.setAttribute('class', 'iso-lbl');
+  tx.setAttribute('font-weight', '500');
+  tx.textContent = label;
+  g.appendChild(tx);
+
+  if (sublabel) {
+    const ts = ns('text');
+    ts.setAttribute('x', x); ts.setAttribute('y', y + hh + 15);
+    ts.setAttribute('text-anchor', 'middle');
+    ts.setAttribute('class', 'iso-sub');
+    ts.textContent = sublabel;
+    g.appendChild(ts);
+  }
+
+  svg.appendChild(g);
+  return {
+    g,
+    cx:      x,
+    cy:      y + hh,
+    top_y:   y,
+    bot_y:   y + hh * 2 + H,
+    left_x:  x - hw,
+    right_x: x + hw,
+  };
+}
+
+function makeArrow(svg) {
+  const defs = ns('defs');
+  const m    = ns('marker');
+  m.setAttribute('id', 'arr');
+  m.setAttribute('viewBox', '0 0 10 10');
+  m.setAttribute('refX', '8'); m.setAttribute('refY', '5');
+  m.setAttribute('markerWidth', '6'); m.setAttribute('markerHeight', '6');
+  m.setAttribute('orient', 'auto-start-reverse');
+  const p = ns('path');
+  p.setAttribute('d', 'M2 1L8 5L2 9');
+  p.setAttribute('fill', 'none');
+  p.style.stroke = 'var(--left-gray)';
+  p.setAttribute('stroke-width', '1.5');
+  p.setAttribute('stroke-linecap', 'round');
+  m.appendChild(p); defs.appendChild(m); svg.insertBefore(defs, svg.firstChild);
+}
+
+function makeLine(svg, x1, y1, x2, y2) {
+  const p = ns('path');
+  const mx = (x1 + x2) / 2, my = Math.min(y1, y2) - 18;
+  p.setAttribute('d', `M${x1},${y1} Q${mx},${my} ${x2},${y2}`);
+  p.classList.add('conn-s');
+  p.style.stroke = 'var(--left-gray)';
+  p.setAttribute('marker-end', 'url(#arr)');
+  svg.appendChild(p);
+}
+
+let state = { parsed: null, viewStack: [] };
+
+function render() {
+  const src = document.getElementById('puml').value;
+  document.getElementById('err').textContent = '';
+  let parsed;
+  try { parsed = parsePuml(src); }
+  catch (e) { document.getElementById('err').textContent = 'Parse error: ' + e.message; return; }
+  state.parsed    = parsed;
+  state.viewStack = [];
+  drawLevel(parsed.root);
+}
+
+function drawLevel(node) {
+  const svg = document.getElementById('iso');
+  svg.innerHTML = '';
+  makeArrow(svg);
+
+  const children = node.children;
+  const conns    = node.conns;
+
+  if (children.length === 0) {
+    svg.setAttribute('viewBox', '0 0 680 100');
+    const t = ns('text');
+    t.setAttribute('x', '340'); t.setAttribute('y', '50');
+    t.setAttribute('text-anchor', 'middle'); t.setAttribute('class', 'iso-sub');
+    t.textContent = 'No nested components.';
+    svg.appendChild(t);
+    updateNav(); return;
+  }
+
+  const W = 80, H = 28;
+  const cols = Math.min(children.length, 4);
+  const rows = Math.ceil(children.length / cols);
+  const vbH  = rows * 160 + 80;
+  svg.setAttribute('viewBox', `0 0 680 ${vbH}`);
+
+  const startX = 340 - (cols - 1) * 90;
+  const positions = {};
+
+  children.forEach((child, i) => {
+    const col = i % cols, row = Math.floor(i / cols);
+    const x = startX + col * 180;
+    const y = 50 + row * 155;
+    const pal      = guessColor(child);
+    const canZoom  = child.children.length > 0;
+    const sub      = canZoom ? 'click to expand →' : null;
+    const blk = makeBlock(svg, x, y, W, H, pal, child.label, sub, canZoom);
+    positions[child.id] = blk;
+
+    if (canZoom) {
+      blk.g.addEventListener('click', () => {
+        state.viewStack.push(node);
+        drawLevel(child);
+      });
+    }
+  });
+
+  conns.forEach(c => {
+    const fp = positions[c.from], tp = positions[c.to];
+    if (!fp || !tp) return;
+    makeLine(svg, fp.cx, fp.bot_y, tp.cx, tp.top_y);
+  });
+
+  updateNav();
+}
+
+function updateNav() {
+  const nav   = document.getElementById('nav');
+  nav.innerHTML = '';
+  const stack = state.viewStack;
+
+  const sep = () => {
+    const s = document.createElement('span');
+    s.className   = 'sep';
+    s.textContent = ' › ';
+    return s;
+  };
+
+  if (stack.length === 0) {
+    const s = document.createElement('span');
+    s.style.color  = 'var(--txt3)';
+    s.textContent  = 'Overview';
+    nav.appendChild(s);
+    return;
+  }
+
+  const overviewEl = document.createElement('span');
+  overviewEl.className   = 'crumb';
+  overviewEl.textContent = 'Overview';
+  overviewEl.onclick     = () => { state.viewStack = []; drawLevel(state.parsed.root); };
+  nav.appendChild(overviewEl);
+
+  stack.forEach((node, i) => {
+    nav.appendChild(sep());
+    if (i < stack.length - 1) {
+      const el = document.createElement('span');
+      el.className   = 'crumb';
+      el.textContent = node.label || node.id;
+      el.onclick     = () => { state.viewStack = stack.slice(0, i); drawLevel(node); };
+      nav.appendChild(el);
+    } else {
+      const el = document.createElement('span');
+      el.style.color = 'var(--txt3)';
+      el.textContent = node.label || node.id;
+      nav.appendChild(el);
+    }
+  });
+
+  nav.appendChild(sep());
+  const cur = stack[stack.length - 1];
+  const curChildren = cur.children;
+  if (curChildren.length > 0) {
+    const el = document.createElement('span');
+    el.style.color = 'var(--txt3)';
+    el.textContent = curChildren[0]?.parent?.label || cur.label;
+    nav.appendChild(el);
+  }
+}
+
+function resetSource() {
+  document.getElementById('puml').value = EXAMPLE;
+  render();
+}
+
+render();
+</script>
+</body>
+</html>