fix split shuffle

src/user_keypad.py

@@ -63,9 +63,13 @@ class UserKeypad:
         self.keypad = dispersed_keypad.reshape(-1)
 
     def split_shuffle(self):
+        # shuffle all keys
+        keypad_view = self.keypad_matrix()
+        np.random.shuffle(keypad_view)
+        # select half the property sets
         prop_permutation = np.random.permutation(self.keypad_size.props_per_key)[: self.keypad_size.props_per_key // 2]
         key_permutation = np.random.permutation(self.keypad_size.numb_of_keys)
-        keypad_view = self.keypad_matrix().copy()
+        # shuffle the selected property sets to new keys as a group
         keypad_view[:, prop_permutation] = keypad_view[key_permutation, :][:, prop_permutation]
         self.keypad = keypad_view.reshape(-1)