Door: New object that change its state between opened and closed after X turns (can be customized), units can pass though when its open, the door will not close when there is a unit inside it
Agressive Effect: Kills any unit inside once it closes, applied to doors only
Linked door effect: links the door's state to another one, this door will not close or open if the other doesn't close or open (Very interesting to make double doors or tunnels) applied to Doors only