diff --git a/sk_demo/src/Mono.cs b/sk_demo/src/Mono.cs
index 5e3c9a2..19d67a8 100644
--- a/sk_demo/src/Mono.cs
+++ b/sk_demo/src/Mono.cs
@@ -1,4 +1,4 @@
-using System.Security.AccessControl;
+using System.Security.AccessControl;
 
 namespace Main;
 public class Mono {
@@ -19,8 +19,6 @@ public class Mono {
   Model model_room = Model.FromFile("room.glb");
   Mesh mesh_room = Mesh.Quad;
 
-  int last_xi = 0;
-
   public class Character {
     public string character;
     public int[] dots;
@@ -212,6 +210,10 @@ public class Mono {
     return layouts[Layout.Colemak][index];
   }
 
+  Matrix keyboard_m4 = Matrix.Identity;
+  Rig.Btn keyboard_btn = new();
+  Vec3 index_pos = Vec3.Zero;
+  int  index_i = 0;
 
   public void Init() {
     rig.Init();
@@ -226,7 +228,11 @@ public class Mono {
   public void Run() {
     rig.Run();
 
-    mat.Run(); // run here or at the end?... or maybe both?
+    keyboard_m4 = Matrix.TRS(
+      V.XYZ(-0.18f, 1.15f, -0.5f),
+      Quat.FromAngles(0, 180, 0) * Quat.FromAngles(40, 0, 0),
+      V.XYZ(-1, -1, 1) * 0.04f
+    );
 
     // thumb extension
     // Matrix palm_ori = rig.hand_1.palm.ToMatrix();
@@ -241,54 +247,47 @@ public class Mono {
       monoNet.send = true;
     }
 
-    int xi = (int)(rig.hand_1.palm.position.x * 25f);
-    xi = Math.Clamp(xi + 4, 0, 26);
+    Vec3 index_tip = keyboard_m4.Inverse * rig.hand_1.Get(FingerId.Index, JointId.Tip).position;
+    // press
+    index_pos.z = Math.Clamp(index_tip.z, -0.3f, 0.1f);
+    keyboard_btn.Frame(index_pos.z > 0.0f, index_pos.z < -0.2f);
 
-    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 (!keyboard_btn.held) {
+      // snap to grid
+      index_pos.x = (float)Math.Clamp(Math.Round(index_tip.x), 0, 10-1);
+      index_pos.y = (float)Math.Clamp(Math.Round(index_tip.y), 0,  3-1);
+
+      index_i = (int)(index_pos.y * 10 + index_pos.x);
     }
 
-    if (xi != last_xi) {
-      Log.Info($"xi: {xi}");
-      last_xi = xi;
-      monoNet.value = xi;
+    if (keyboard_btn.frameDown) {
+      Log.Info($"index_i: {index_i}");
+      monoNet.value = index_i;
       monoNet.send = true;
     }
 
     // keyboard
-    Matrix keyboard_m4 = Matrix.TRS(
-      rig.head_pos + V.XYZ(0, -0.1f, -0.2f),
-      rig.head_ori * Quat.FromAngles(0, 180, 0),
-      0.2f
-    );
     Hierarchy.Push(keyboard_m4);
     // 3 rows of 10 keys
-    for (int i = 0; i < 3; i++) {
-      for (int j = 0; j < 10; j++) {
+    for (int y = 0; y < 3; y++) {
+      for (int x = 0; x < 10; x++) {
+        Vec3 pos = V.XYZ(x, y, 0);
         // background quad
         Mesh.Quad.Draw(
           mat.unlit_clear,
-          Matrix.TRS(
-            V.XYZ(j * -0.1f, i * -0.1f, 0.0f) + V.XYZ(0.45f, 0.0f, 0.0f),
-            Quat.FromAngles(0, 0, 0),
-            0.09f
-          ),
-          Color.Hex(0x00000020)
+          Matrix.TS(pos, 0.9f),
+          Color.Hex(0x00000040)
         );
 
-        int index = i * 10 + j;
+        int index = y * 10 + x;
         // string text = characters[index].character;
         string keychar = KeyToChar(index);
 
         Text.Add(
           keychar,
           Matrix.TS(
-            V.XYZ(j * -0.1f, i * -0.1f, 0.0f) + V.XYZ(0.45f, 0.0f, 0.0f),
-            1.0f
+            pos + V.XYZ(-0.3f, -0.3f, 0),
+            V.XYZ(-1, -1, 0) * 8.0f
           ),
           TextAlign.Center,
           TextAlign.Center,
@@ -296,17 +295,17 @@ public class Mono {
         );
         // show the braille dots(spheres) above the text
         for (int k = 0; k < 6; k++) {
-          float spacing = 0.02f;
+          float spacing = 0.2f;
           float x_offset = (k % 2) * spacing;
           float y_offset = (k / 2) * -spacing;
           if (char_cell[keychar][k] == 1) {
             Mesh.Sphere.Draw(
               mat.unlit_clear,
               Matrix.TS(
-                V.XYZ(j * -0.1f - x_offset, i * -0.1f + y_offset, 0.0f) + V.XYZ(0.45f + 0.01f, 0.018f, 0.0f),
-                0.01f
+                V.XYZ(pos.x + x_offset, pos.y - y_offset, 0) + V.XYZ(-0.1f, -0.18f, 0),
+                0.1f
               ),
-              Color.Hex(0x80808040)
+              Color.Hex(0xFFFFFFFF)
             );
           }
         }
@@ -314,6 +313,16 @@ public class Mono {
     }
     Hierarchy.Pop();
 
+    // keyboard button
+    Mesh.Cube.Draw(
+      mat.unlit_clear,
+      Matrix.TS(
+        index_pos * V.XYZ(1, 1, 0.25f),
+        V.XYZ(0.8f, 0.8f, -index_pos.z * 0.5f)
+      ) * keyboard_m4,
+      keyboard_btn.held ? Color.Hex(0x00000090) : Color.Hex(0x80808090)
+    );
+
     // WORLD
     mesh_room.Draw(
       mat_room,
@@ -335,5 +344,7 @@ public class Mono {
       V.XYZ(2, 2f, 2f) * U.cm,
       V.XYZ(0, 0, 0)
     };
+
+    mat.Run();
   }
 }
\ No newline at end of file