Earth attacked the army of alien robots. They fell on the ships, cut off all electronic systems that completely paralyzed the life of the planet. People are not able to react quickly and fight back, and landed the aggressors managed to hide in different buildings, hatching new plans to capture. Since modern weapons does not work, it is necessary to use a medieval, but it is - a big catapult, like a slingshot. Charge it with stones and shoot to kill a robot destroyed walls.