diff --git a/sk_demo/src/Mono.cs b/sk_demo/src/Mono.cs
index fc794e4..4d02a6d 100644
--- a/sk_demo/src/Mono.cs
+++ b/sk_demo/src/Mono.cs
@@ -228,6 +228,14 @@ public class Mono {
 
     mat.Run(); // run here or at the end?... or maybe both?
 
+    // thumb extension
+    // Matrix palm_ori = rig.hand_1.palm.ToMatrix();
+    // Vec3 thumb_tip = palm_ori.Inverse * rig.hand_1.Get(FingerId.Thumb, JointId.Tip).position;
+    // Vec3 thumb_minor = palm_ori.Inverse * rig.hand_1.Get(FingerId.Thumb, JointId.KnuckleMinor).position;
+    // if (thumb_tip.x < thumb_minor.x - 0f * U.cm) {
+    //   // Log.Info("thumb is out");
+    //   xi = 0;
+    // }
     if (Input.Key(Key.Down).IsJustActive()) {
       monoNet.value = 0;
       monoNet.send = true;