English: You need a object that you can hold(as gun) and that has a color that isn't alrady in the room you are playing in(e.g a piece of colored paper, in my case green works pretty good) At the beginning click on the object that you decided to use as gun, move it around and click again and repeat this process until the aim point follows it when you move the gun. Then press space to start the game, there will be little monsters walking to you that you have to shoot down. press space to shoot(you have a cooldown of 3 seconds)
This was finally an idea by me XD This is a shooter where you aim with a real object.