diff --git a/playground/a-immersive.html b/playground/a-immersive.html
index d1e1e5a..32f6cb0 100644
--- a/playground/a-immersive.html
+++ b/playground/a-immersive.html
@@ -207,7 +207,7 @@
           <span class="mode-label">Output</span>
           <div class="pill-toggle pill-toggle-sm" id="output-toggle-float">
             <button class="pill-opt active" data-mode="visual">Visual</button>
-            <button class="pill-opt" data-mode="synth">Synth</button>
+            <button class="pill-opt" data-mode="synth" id="synth-mode-btn">C15 Shaper-Feedback</button>
             <button class="pill-opt" data-mode="midi-cc">MIDI CC</button>
             <button class="pill-opt" data-mode="audio-canvas">Audio Canvas</button>
           </div>
diff --git a/playground/js/a-app.js b/playground/js/a-app.js
index 8b83e64..1bef9d9 100644
--- a/playground/js/a-app.js
+++ b/playground/js/a-app.js
@@ -740,6 +740,8 @@ async function setActiveEngine(engine) {
   activeEngine = engine;
   c15 = engine; // keep alias in sync
   arpeggiator.setEngine(engine);
+  const btn = document.getElementById('synth-mode-btn');
+  if (btn) btn.textContent = engine.displayName;
   await resizeMLP(engine.paramCount);
 }