(I am new to BGE so I might sound like a noob) I am making a game with two doors in it. One is open and the other is closed. When you press the spacebar, the one that was open will close and the one that was closed will open. I have no idea how to do this. Can I get some help?


1 Answer 1


As you want to use the same event for both opening and closing I suggest to implement a state machine.

State machine

The states are at least:

  • Closed,
  • Opened

The transitions are:

  • Closed:

    • on space: transit to Opened
  • Opened:

    • on space: transit to Closed

Entry Actions:

  • Closed:

    • play closing action
  • Opened:

    • play closing action



We use a boolean property as current state. Call it "opened". When True it means status Open, when False it means status Closed.

Property: "opened" Type: Boolean Value: unchecked

Transition logic

Property Sensor -> AND -> Action Actuator

Property Sensor Mode: equal Property: opened Value: False

I assume you want to play the same animation reverse on closing

Action Actuator Mode: Flipper Action: opening animation

What will happen?

When opened is False, the sensor does nothing and the door remains as it is (closed). When the property opened turns True, the sensor triggers the AND controller which activates the action actuator. The action actuator begins to open the door till it is completely open.

When the property opened turns False, the sensor triggers the AND controller which deactivates the action actuator. The action actuator begins to play the opening animation reverse -> closing the door till it is closed.

Event logic

Now you need a way to switch the property.

keyboard sensor -> AND -> Property actuator

Keyboard sensor Key: space

Property Actuator Mode: toggle Property: opened

What it does: when you press space the sensor will trigger the AND which will activate the Property actuator. The property actuator will toggle the property opened (from True to False and False to True).

This will be the event on the above Transition logic, which will play the according animation.


There are other ways to implement door logic. This is just a sample.


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