diff --git a/playground/a-immersive.html b/playground/a-immersive.html
index 79ad01f..4ccddb1 100644
--- a/playground/a-immersive.html
+++ b/playground/a-immersive.html
@@ -110,6 +110,7 @@
 
   <!-- RL floating buttons (with undo between/below) -->
   <div class="rl-buttons" id="rl-buttons">
+    <span class="rl-label hidden" id="rl-label">Synth</span>
     <button class="rl-btn rl-down" id="btn-thumbsdown" title="Explore more"><span class="rl-icon">&minus;</span><span class="key-num">1</span></button>
     <button class="rl-btn rl-up" id="btn-thumbsup" title="Keep this"><span class="rl-icon">+</span><span class="key-num">2</span></button>
     <button class="rl-undo-btn" id="btn-undo" title="Undo last action">
@@ -119,6 +120,13 @@
     </button>
   </div>
 
+  <!-- EOC RL buttons (shown only in Linked mode) -->
+  <div id="eoc-rl-buttons" class="eoc-rl-buttons hidden">
+    <span class="eoc-rl-label">FX</span>
+    <button id="eoc-rl-minus" class="rl-btn eoc-rl-btn rl-down" title="Explore FX (change effects)"><span class="rl-icon">&minus;</span><span class="key-num">3</span></button>
+    <button id="eoc-rl-plus" class="rl-btn eoc-rl-btn rl-up" title="Keep FX (reinforce effects)"><span class="rl-icon">+</span><span class="key-num">4</span></button>
+  </div>
+
   <!-- Status line (floating, minimal) -->
   <div class="status-line" id="status-line">
     <span id="status-text">0 examples &middot; untrained</span>
@@ -371,6 +379,8 @@
           <tr><th colspan="2">Keyboard</th></tr>
           <tr><td><kbd>1</kbd></td><td>Negative feedback (&minus;)</td></tr>
           <tr><td><kbd>2</kbd></td><td>Positive feedback (+)</td></tr>
+          <tr><td><kbd>3</kbd></td><td>FX negative feedback (Linked mode)</td></tr>
+          <tr><td><kbd>4</kbd></td><td>FX positive feedback (Linked mode)</td></tr>
           <tr><td><kbd>Z</kbd></td><td>Undo</td></tr>
           <tr><th colspan="2">Gamepad (Steam Deck, Xbox, etc.)</th></tr>
           <tr><td>Left stick</td><td>Joystick control</td></tr>
diff --git a/playground/css/a-immersive.css b/playground/css/a-immersive.css
index 98ee391..f3be6c1 100644
--- a/playground/css/a-immersive.css
+++ b/playground/css/a-immersive.css
@@ -634,6 +634,67 @@ html, body {
   animation: rl-flash 0.25s ease-out;
 }
 
+/* ---- RL label (shown in Linked mode to distinguish Synth vs FX) ---- */
+.rl-label {
+  grid-column: 1 / -1;
+  font-size: 10px;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  opacity: 0.6;
+  text-align: center;
+  color: var(--text);
+}
+.rl-label.hidden { display: none; }
+
+/* ---- EOC RL buttons (FX feedback, Linked mode) ---- */
+.eoc-rl-buttons {
+  position: fixed;
+  bottom: 36px;
+  left: calc(50% + 100px);
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 6px;
+  z-index: 45;
+  transition: opacity 0.3s;
+}
+.eoc-rl-buttons.hidden { display: none; }
+
+.eoc-rl-label {
+  font-size: 10px;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  opacity: 0.6;
+  color: var(--text);
+}
+
+.eoc-rl-btn {
+  width: 48px;
+  height: 48px;
+}
+
+.eoc-rl-btn.rl-up {
+  border-color: rgba(78, 205, 196, 0.4);
+  color: #4ecdc4;
+  background: rgba(78, 205, 196, 0.08);
+}
+
+.eoc-rl-btn.rl-up:active {
+  background: rgba(78, 205, 196, 0.2);
+  box-shadow: 0 0 20px rgba(78, 205, 196, 0.3);
+}
+
+.eoc-rl-btn.rl-down {
+  border-color: rgba(78, 205, 196, 0.3);
+  color: #e07040;
+  background: rgba(224, 112, 64, 0.08);
+}
+
+.eoc-rl-btn.rl-down:active {
+  background: rgba(224, 112, 64, 0.2);
+  box-shadow: 0 0 20px rgba(224, 112, 64, 0.3);
+}
+
 /* ---- Status line (floating, minimal) ---- */
 .status-line {
   position: fixed;
@@ -1956,6 +2017,11 @@ html, body {
     font-size: 32px;
   }
 
+  .eoc-rl-btn {
+    width: 54px;
+    height: 54px;
+  }
+
   .drawer-stack {
     width: 280px;
   }
@@ -1985,6 +2051,15 @@ html, body {
   .rl-icon {
     font-size: 24px;
   }
+
+  .eoc-rl-btn {
+    width: 42px;
+    height: 42px;
+  }
+
+  .eoc-rl-buttons {
+    left: calc(50% + 80px);
+  }
 }
 
 /* ---- MIDI CC mode ---- */
diff --git a/playground/js/a-app.js b/playground/js/a-app.js
index 5453317..9230478 100644
--- a/playground/js/a-app.js
+++ b/playground/js/a-app.js
@@ -1112,6 +1112,13 @@ async function init() {
         await initEocIML();
       }
     }
+
+    // Show/hide EOC RL buttons and Synth label based on linked mode
+    const isLinked = eocChain.nispsMode === 'linked';
+    const eocRlContainer = document.getElementById('eoc-rl-buttons');
+    if (eocRlContainer) eocRlContainer.classList.toggle('hidden', !isLinked);
+    const rlLabel = document.getElementById('rl-label');
+    if (rlLabel) rlLabel.classList.toggle('hidden', !isLinked);
   });
 
   // Debug probe — exposed on window when ?debug=1 is in the URL.
@@ -2003,6 +2010,28 @@ function wireControls() {
   $btnThumbsUp.addEventListener('click', onThumbsUp);
   $btnThumbsDown.addEventListener('click', onThumbsDown);
 
+  // EOC RL buttons (Linked mode — target EOC IML directly)
+  const eocRlPlus = document.getElementById('eoc-rl-plus');
+  const eocRlMinus = document.getElementById('eoc-rl-minus');
+  if (eocRlPlus && eocRlMinus) {
+    eocRlPlus.addEventListener('click', () => {
+      if (!imlEoc) return;
+      const prevTarget = eocTrainingTarget;
+      eocTrainingTarget = 'eoc';
+      onThumbsUp();
+      eocTrainingTarget = prevTarget;
+      flash('eoc-rl-plus');
+    });
+    eocRlMinus.addEventListener('click', () => {
+      if (!imlEoc) return;
+      const prevTarget = eocTrainingTarget;
+      eocTrainingTarget = 'eoc';
+      onThumbsDown();
+      eocTrainingTarget = prevTarget;
+      flash('eoc-rl-minus');
+    });
+  }
+
   // Undo button
   document.getElementById('btn-undo').addEventListener('click', onUndo);
 
@@ -3056,6 +3085,24 @@ function wireKeyboard() {
     } else if (e.key === '2' || e.code === 'Numpad2') {
       e.preventDefault();
       onThumbsUp();
+    } else if (e.key === '3' || e.code === 'Numpad3') {
+      e.preventDefault();
+      if (imlEoc && eocChain?.nispsMode === 'linked') {
+        const prevTarget = eocTrainingTarget;
+        eocTrainingTarget = 'eoc';
+        onThumbsDown();
+        eocTrainingTarget = prevTarget;
+        flash('eoc-rl-minus');
+      }
+    } else if (e.key === '4' || e.code === 'Numpad4') {
+      e.preventDefault();
+      if (imlEoc && eocChain?.nispsMode === 'linked') {
+        const prevTarget = eocTrainingTarget;
+        eocTrainingTarget = 'eoc';
+        onThumbsUp();
+        eocTrainingTarget = prevTarget;
+        flash('eoc-rl-plus');
+      }
     } else if (e.key === 'z' || e.key === 'Z') {
       e.preventDefault();
       onUndo();