code: function (evt) {
      var button = this.mapping.buttons[evt.detail.id];
      var buttonMeshes = this.buttonMeshes;
      var analogValue;
  
      if (!button) { return; }
  
      if (button === 'trigger') {
        analogValue = evt.detail.state.value;
        // Update trigger rotation depending on button value.
        if (buttonMeshes && buttonMeshes.trigger) {
          buttonMeshes.trigger.rotation.x = -analogValue * (Math.PI / 12);
        }
      }
  
      // Pass along changed event with button state, using button mapping for convenience.
      this.el.emit(button + 'changed', evt.detail.state);
    }
docs: Rotate the trigger button based on how hard the trigger is pressed.