Algodoo

Fires seven exotic projectiles that fly perfectly straight and never stop. They can be reflected by a strong enough obstacle, but they do not stop going.

A and D to aim, F to fire. Don`t hold it for more than half a second or so. Does not fire rapidly; you need to wait three seconds between shots, although the gun may still function correctly if you speed up the piston wheel a bit (The piston wheel, which reloads the gun, is the bottleneck in the system).