refactor(shapeseq): restore arpeggiator, gate ShapeSeq behind ?shapeseq=1

Restore the original arpeggiator as the default sequencer. ShapeSeq
code is preserved but gated behind a URL feature flag (?shapeseq=1):

- Arpeggiator import, state, and all wiring fully restored
- ShapeSeq modules loaded via dynamic import() only when flag is on
- ensureShapeSeqInit() creates engine/viz/UI lazily on first audio start
- animate loop routes inputs to ShapeSeq only when flag + playing
- setOutputMode shows/hides ShapeSeq container only when flag is on
- HTML: ShapeSeq container added but hidden by default
- CSS: ShapeSeq styles added (inert when container is hidden)

All 13 ShapeSeq modules in playground/js/shapeseq/ are untouched.
To test ShapeSeq: add ?shapeseq=1 to the URL.

playground/a-immersive.html

@@ -21,7 +21,7 @@
 
   <!-- Synth quick controls (play button + drawer, next to back button) -->
   <div class="synth-quick-controls hidden" id="synth-quick-controls">
-    <button class="play-btn" id="quick-play" title="Start audio + sequencer">
+    <button class="play-btn" id="quick-play" title="Start audio + arpeggiator">
       <svg width="16" height="16" viewBox="0 0 16 16" fill="currentColor" id="quick-play-icon"><path d="M4 2l10 6-10 6z"/></svg>
     </button>
     <div class="play-drawer" id="play-drawer">
@@ -60,7 +60,7 @@
   <!-- Synth visualization canvas -->
   <canvas id="synth-vis-canvas"></canvas>
 
-  <!-- ShapeSeq UI (synth mode only) -->
+  <!-- ShapeSeq UI (hidden by default, enabled with ?shapeseq=1) -->
   <div class="shapeseq-container hidden" id="shapeseq-container">
     <canvas id="shapeseq-viz"></canvas>
     <div class="shapeseq-chain-wrap" id="shapeseq-chain"></div>
@@ -157,16 +157,29 @@
           <input type="range" id="synth-volume" min="0" max="1" step="0.01" value="0.5">
         </div>
         <div class="synth-row">
-          <label>Sequencer</label>
+          <label>Arpeggiator</label>
-          <button class="action-btn" id="seq-toggle">Play</button>
+          <button class="action-btn" id="arp-toggle">Play</button>
+        </div>
+        <div class="synth-row">
+          <label>Progression</label>
+          <select id="arp-progression">
+            <option value="I-vi-IV-V">I-vi-IV-V</option>
+            <option value="I-IV-vi-V">I-IV-vi-V</option>
+            <option value="i-VI-III-VII">i-VI-III-VII</option>
+            <option value="I-V-vi-IV">I-V-vi-IV</option>
+          </select>
         </div>
         <div class="synth-row">
           <label>Tempo <span id="tempo-val">120</span></label>
-          <input type="range" id="seq-tempo" min="40" max="240" step="1" value="120">
+          <input type="range" id="arp-tempo" min="40" max="240" step="1" value="120">
         </div>
         <div class="synth-row">
-          <label>Steps <span id="steps-val">8</span></label>
+          <label>Octaves <span id="octaves-val">2</span></label>
-          <input type="range" id="seq-steps" min="1" max="32" step="1" value="8">
+          <input type="range" id="arp-octaves" min="1" max="5" step="1" value="2">
+        </div>
+        <div class="synth-row">
+          <label>Oct Offset <span id="offset-val">0</span></label>
+          <input type="range" id="arp-offset" min="-2" max="3" step="1" value="0">
         </div>
         <div class="synth-row" id="midi-row" style="display:none">
           <label>MIDI Input</label>
@@ -286,7 +299,7 @@
             <li><strong>Mute (M)</strong> &mdash; removes the parameter from NISPS control; its bar disappears and you get a manual value slider instead</li>
           </ul>
           <li><strong>MIDI input</strong> &mdash; connect a MIDI controller and it will be detected automatically; MIDI notes trigger the synth directly</li>
-          <li><strong>ShapeSeq</strong> &mdash; in synth mode, the sequencer UI appears: a circular step visualizer shows the current pattern; the chain builder below lets you add/remove/reorder algorithmic primitives; press Play to start the generative sequencer</li>
+          <li><strong>Arpeggiator</strong> &mdash; expand the bottom bar to access the built-in arpeggiator with tempo, octave range, offset, and chord progression controls; press Pause to stop it</li>
         </ul>
       </div>
 

playground/css/a-immersive.css

@@ -98,7 +98,7 @@ html, body {
   display: none;
 }
 
-/* ---- ShapeSeq container (synth mode) ---- */
+/* ---- ShapeSeq container (synth mode, feature-flagged) ---- */
 .shapeseq-container {
   position: fixed;
   inset: 0;
@@ -108,17 +108,8 @@ html, body {
   background: #0d0d0d;
   overflow: hidden;
 }
-
+.shapeseq-container.hidden { display: none; }
-.shapeseq-container.hidden {
+#shapeseq-viz { width: 100%; flex: 0 0 45%; min-height: 0; }
-  display: none;
-}
-
-#shapeseq-viz {
-  width: 100%;
-  flex: 0 0 45%;
-  min-height: 0;
-}
-
 .shapeseq-chain-wrap {
   flex: 1 1 auto;
   overflow-y: auto;
@@ -1035,7 +1026,6 @@ html, body {
   transition: background 0.15s, border-color 0.15s;
   padding: 0;
   flex-shrink: 0;
-  align-self: flex-start;
 }
 
 .play-btn:active {
@@ -1101,8 +1091,7 @@ html, body {
   color: var(--text-dim);
 }
 
-.play-btn:hover ~ .play-drawer,
+.synth-quick-controls:hover .play-drawer,
-.play-drawer:hover,
 .play-drawer.show {
   display: flex;
 }
@@ -1131,7 +1120,6 @@ html, body {
   min-width: 0;
   max-width: 160px;
   text-overflow: ellipsis;
-  align-self: flex-start;
 }
 
 .preset-select:hover,

playground/js/a-app.js

@@ -4,11 +4,31 @@
 import { WasmIML } from './nisps/nisps-wasm.js';
 import { FlowFieldVisualizer } from './ui/visualizer.js';
 import { C15Bridge } from './synth/c15-bridge.js';
-import { ShapeSeqEngine } from './shapeseq/sequencer.js';
+import { Arpeggiator } from './synth/arpeggiator.js';
-import { StepVisualizer } from './shapeseq/step-viz.js';
-import { ChainBuilderUI } from './shapeseq/chain-ui.js';
-import { getDefaultBus } from './shapeseq/event-bus.js';
 import { MIDIInput } from './synth/midi-input.js';
+
+// ---- ShapeSeq (feature-flagged, enable with ?shapeseq=1) ----
+const ENABLE_SHAPESEQ = new URLSearchParams(window.location.search).get('shapeseq') === '1';
+let _shapeSeqImports = null;
+async function getShapeSeqModules() {
+  if (_shapeSeqImports) return _shapeSeqImports;
+  const [seqMod, vizMod, uiMod, busMod] = await Promise.all([
+    import('./shapeseq/sequencer.js'),
+    import('./shapeseq/step-viz.js'),
+    import('./shapeseq/chain-ui.js'),
+    import('./shapeseq/event-bus.js'),
+  ]);
+  _shapeSeqImports = {
+    ShapeSeqEngine: seqMod.ShapeSeqEngine,
+    StepVisualizer: vizMod.StepVisualizer,
+    ChainBuilderUI: uiMod.ChainBuilderUI,
+    getDefaultBus: busMod.getDefaultBus,
+  };
+  return _shapeSeqImports;
+}
+let shapeSeq = null;
+let stepViz = null;
+let chainUI = null;
 import { SYNTH_PARAM_MAP, SYNTH_PARAM_NAMES, SYNTH_PARAM_COLORS, applyCurve, applyGroupOverride } from './synth/param-map.js';
 import { GamepadInput } from './ui/gamepad.js';
 import { HandTracker } from './ui/hand-tracker.js';
@@ -76,9 +96,7 @@ let handTracker = null;
 let visualizer;
 let synthVisualizer;
 let c15 = null;
-let shapeSeq = null;      // ShapeSeqEngine instance
+let arpeggiator = null;
-let stepViz = null;       // StepVisualizer
-let chainUI = null;       // ChainBuilderUI
 let midiInput = null;
 
 let outputMode = 'visual';
@@ -708,9 +726,7 @@ async function init() {
     if (el) el.textContent = msg;
   };
   c15.loadParams();
-
+  arpeggiator = new Arpeggiator(c15);
-  // ShapeSeq is initialized lazily when audio starts (needs AudioContext)
-
   midiInput = new MIDIInput(c15);
   initMIDIControls();
 
@@ -759,7 +775,6 @@ async function init() {
   wireQuickPlayControls();
   wireGroupDrawer();
   wireHelp();
-  wireShapeSeqControls();
 
   // Resize
   window.addEventListener('resize', onResize);
@@ -1309,6 +1324,7 @@ function setOutputMode(mode) {
 
   const heatmapStrip = document.getElementById('heatmap-strip');
   const synthQuickControls = document.getElementById('synth-quick-controls');
+
   const shapeseqContainer = document.getElementById('shapeseq-container');
 
   if (mode === 'synth') {
@@ -1318,19 +1334,20 @@ function setOutputMode(mode) {
     heatmapStrip.classList.add('hidden');
     synthQuickControls.classList.remove('hidden');
     synthVisualizer.enableInteraction(true);
-    // Show ShapeSeq UI
-    if (shapeseqContainer) shapeseqContainer.classList.remove('hidden');
-    // Resize step viz canvas to fit its container
-    if (stepViz) {
-      const vizCanvas = document.getElementById('shapeseq-viz');
-      if (vizCanvas) {
-        const rect = vizCanvas.getBoundingClientRect();
-        stepViz.resize(rect.width, rect.height);
-      }
-    }
     // Pulse play button if audio not yet started
     const qp = document.getElementById('quick-play');
     if (qp) qp.classList.toggle('audio-needs-init', !(c15 && c15.running));
+    // Show ShapeSeq UI if feature-flagged
+    if (ENABLE_SHAPESEQ && shapeseqContainer) {
+      shapeseqContainer.classList.remove('hidden');
+      if (stepViz) {
+        const vizCanvas = document.getElementById('shapeseq-viz');
+        if (vizCanvas) {
+          const rect = vizCanvas.getBoundingClientRect();
+          stepViz.resize(rect.width, rect.height);
+        }
+      }
+    }
   } else {
     $synthPanel.classList.add('hidden');
     $canvas.classList.remove('hidden-canvas');
@@ -1588,41 +1605,47 @@ function syncRawParamsFromOutputs(outputs) {
   });
 }
 
-// ---- ShapeSeq lazy init (needs AudioContext from C15) ----
+// ---- ShapeSeq lazy init (feature-flagged) ----
 async function ensureShapeSeqInit() {
-  if (shapeSeq) return; // already initialized
+  if (!ENABLE_SHAPESEQ) return;
-  if (!c15 || !c15.audioContext) return; // no audio context yet
+  if (shapeSeq) return;
-
+  if (!c15 || !c15.audioContext) return;
-  const eventBus = getDefaultBus(c15.audioContext);
+  try {
-  shapeSeq = new ShapeSeqEngine({ audioContext: c15.audioContext, eventBus, c15Bridge: c15 });
+    const mods = await getShapeSeqModules();
-  await shapeSeq.init();
+    const eventBus = mods.getDefaultBus(c15.audioContext);
-
+    shapeSeq = new mods.ShapeSeqEngine({ audioContext: c15.audioContext, eventBus, c15Bridge: c15 });
-  // Wire up StepVisualizer and ChainBuilderUI now that engine exists
+    await shapeSeq.init();
-  const seqVizCanvas = document.getElementById('shapeseq-viz');
+    const seqVizCanvas = document.getElementById('shapeseq-viz');
-  const seqChainContainer = document.getElementById('shapeseq-chain');
+    const seqChainContainer = document.getElementById('shapeseq-chain');
-  if (seqVizCanvas && !stepViz) {
+    if (seqVizCanvas && !stepViz) {
-    stepViz = new StepVisualizer({ canvas: seqVizCanvas, eventBus });
+      stepViz = new mods.StepVisualizer({ canvas: seqVizCanvas, eventBus });
-    const rect = seqVizCanvas.getBoundingClientRect();
+      const rect = seqVizCanvas.getBoundingClientRect();
-    if (rect.width > 0 && rect.height > 0) stepViz.resize(rect.width, rect.height);
+      if (rect.width > 0 && rect.height > 0) stepViz.resize(rect.width, rect.height);
+    }
+    if (seqChainContainer && !chainUI) {
+      chainUI = new mods.ChainBuilderUI({ container: seqChainContainer, chain: shapeSeq.getChain(), eventBus });
+    }
+    console.log('[NISPS] ShapeSeq initialized');
+  } catch (err) {
+    console.error('[NISPS] ShapeSeq init failed:', err);
   }
-  if (seqChainContainer && !chainUI) {
-    chainUI = new ChainBuilderUI({ container: seqChainContainer, chain: shapeSeq.getChain(), eventBus });
-  }
-
-  console.log('[NISPS] ShapeSeq initialized');
 }
 
 // ---- Synth controls ----
 function wireSynthControls() {
   const startBtn = document.getElementById('synth-start');
   const volumeSlider = document.getElementById('synth-volume');
+  const arpToggle = document.getElementById('arp-toggle');
+  const arpProgression = document.getElementById('arp-progression');
+  const arpTempo = document.getElementById('arp-tempo');
+  const arpOctaves = document.getElementById('arp-octaves');
+  const arpOffset = document.getElementById('arp-offset');
 
   startBtn.addEventListener('click', async () => {
     const quickPlay = document.getElementById('quick-play');
     if (c15.running) {
-      if (shapeSeq) shapeSeq.stop();
+      arpeggiator.stop();
-      const seqToggle = document.getElementById('seq-toggle');
+      arpToggle.textContent = 'Play';
-      if (seqToggle) seqToggle.textContent = 'Play';
       await c15.stop();
       startBtn.textContent = 'Start Audio';
       if (quickPlay) quickPlay.classList.add('audio-needs-init');
@@ -1641,48 +1664,42 @@ function wireSynthControls() {
     if (quickVol) quickVol.value = e.target.value;
   });
 
-}
+  arpToggle.addEventListener('click', () => {
+    if (!c15.running) return;
+    if (arpeggiator.playing) {
+      arpeggiator.stop();
+      arpToggle.textContent = 'Play';
+    } else {
+      arpeggiator.start();
+      arpToggle.textContent = 'Stop';
+    }
+  });
 
-// ---- ShapeSeq controls (bottom sheet) ----
+  arpProgression.addEventListener('change', (e) => {
-function wireShapeSeqControls() {
+    arpeggiator.progression = e.target.value;
-  const seqToggle = document.getElementById('seq-toggle');
+  });
-  const seqTempo = document.getElementById('seq-tempo');
-  const seqSteps = document.getElementById('seq-steps');
 
-  if (seqToggle) {
+  arpTempo.addEventListener('input', (e) => {
-    seqToggle.addEventListener('click', async () => {
+    const val = parseInt(e.target.value);
-      if (!c15.running) return;
+    arpeggiator.bpm = val;
-      await ensureShapeSeqInit();
+    document.getElementById('tempo-val').textContent = val;
-      if (!shapeSeq) return;
+    const quickBpm = document.getElementById('quick-bpm');
-      if (shapeSeq.isPlaying) {
+    const quickBpmVal = document.getElementById('quick-bpm-val');
-        if (shapeSeq) shapeSeq.stop();
+    if (quickBpm) quickBpm.value = val;
-        seqToggle.textContent = 'Play';
+    if (quickBpmVal) quickBpmVal.textContent = val;
-      } else {
+  });
-        shapeSeq.start();
-        seqToggle.textContent = 'Stop';
-      }
-    });
-  }
 
-  if (seqTempo) {
+  arpOctaves.addEventListener('input', (e) => {
-    seqTempo.addEventListener('input', (e) => {
+    const val = parseInt(e.target.value);
-      const val = parseInt(e.target.value);
+    arpeggiator.octaves = val;
-      if (shapeSeq) shapeSeq.setTempo(val);
+    document.getElementById('octaves-val').textContent = val;
-      document.getElementById('tempo-val').textContent = val;
+  });
-      const quickBpm = document.getElementById('quick-bpm');
-      const quickBpmVal = document.getElementById('quick-bpm-val');
-      if (quickBpm) quickBpm.value = val;
-      if (quickBpmVal) quickBpmVal.textContent = val;
-    });
-  }
 
-  if (seqSteps) {
+  arpOffset.addEventListener('input', (e) => {
-    seqSteps.addEventListener('input', (e) => {
+    const val = parseInt(e.target.value);
-      const val = parseInt(e.target.value);
+    arpeggiator.octaveOffset = val;
-      if (shapeSeq) shapeSeq.setStepCount(val);
+    document.getElementById('offset-val').textContent = val;
-      document.getElementById('steps-val').textContent = val;
+  });
-    });
-  }
 }
 
 // ---- MIDI Input ----
@@ -1826,23 +1843,23 @@ function wireQuickPlayControls() {
 
   quickPlay.addEventListener('click', async () => {
     if (c15.running) {
-      if (shapeSeq) shapeSeq.stop();
+      arpeggiator.stop();
       await c15.stop();
       // Also update the bottom sheet controls
       const startBtn = document.getElementById('synth-start');
-      const seqToggle = document.getElementById('seq-toggle');
+      const arpToggle = document.getElementById('arp-toggle');
       if (startBtn) startBtn.textContent = 'Start Audio';
-      if (seqToggle) seqToggle.textContent = 'Play';
+      if (arpToggle) arpToggle.textContent = 'Play';
     } else {
       await c15.start();
       await ensureShapeSeqInit();
-      if (shapeSeq) shapeSeq.start();
+      arpeggiator.start();
       routeOutputs(iml.getOutputs());
       // Also update the bottom sheet controls
       const startBtn = document.getElementById('synth-start');
-      const seqToggle = document.getElementById('seq-toggle');
+      const arpToggle = document.getElementById('arp-toggle');
       if (startBtn) startBtn.textContent = 'Stop Audio';
-      if (seqToggle) seqToggle.textContent = 'Stop';
+      if (arpToggle) arpToggle.textContent = 'Stop';
     }
     updatePlayIcon();
   });
@@ -1856,10 +1873,10 @@ function wireQuickPlayControls() {
 
   quickBpm.addEventListener('input', (e) => {
     const val = parseInt(e.target.value);
-    if (shapeSeq) shapeSeq.setTempo(val);
+    arpeggiator.bpm = val;
     quickBpmVal.textContent = val;
     // Sync with bottom sheet tempo slider
-    const sheetTempo = document.getElementById('seq-tempo');
+    const sheetTempo = document.getElementById('arp-tempo');
     const sheetTempoVal = document.getElementById('tempo-val');
     if (sheetTempo) sheetTempo.value = val;
     if (sheetTempoVal) sheetTempoVal.textContent = val;
@@ -2192,13 +2209,11 @@ function onResize() {
   synthVisualizer.resize();
 
   // Resize ShapeSeq step viz if visible
-  if (stepViz && outputMode === 'synth') {
+  if (ENABLE_SHAPESEQ && stepViz && outputMode === 'synth') {
     const vizCanvas = document.getElementById('shapeseq-viz');
     if (vizCanvas) {
       const rect = vizCanvas.getBoundingClientRect();
-      if (rect.width > 0 && rect.height > 0) {
+      if (rect.width > 0 && rect.height > 0) stepViz.resize(rect.width, rect.height);
-        stepViz.resize(rect.width, rect.height);
-      }
     }
   }
 
@@ -2235,15 +2250,15 @@ function animate() {
   if (gamepad) gamepad.poll();
   if (outputMode === 'synth') {
     synthVisualizer.draw();
-    // Route inputs to ShapeSeq and render step viz
+    // ShapeSeq: route inputs and render step viz (feature-flagged)
-    if (shapeSeq && shapeSeq.isPlaying) {
+    if (ENABLE_SHAPESEQ && shapeSeq && shapeSeq.isPlaying) {
       if (inputMode === 'hands' && handTracker && handTracker.active && handTracker.features) {
         shapeSeq.setSequenceInputs([handTracker.features[0], handTracker.features[1]]);
       } else {
         shapeSeq.setSequenceInputs([joyX, joyY]);
       }
     }
-    if (stepViz) stepViz.render();
+    if (ENABLE_SHAPESEQ && stepViz) stepViz.render();
   } else {
     visualizer.draw();
   }