Imagine having to protect your home, town, country against a cavalcade of enemies. You need to cut transmission ways. You can use only a few automatic guns which emit bullets. You can place them in very few places. You know that if you allow your enemy to transport enough goods, your enemy becomes stronger and stronger. If you want to protect your habitat, you have to organise ambushes. On each level your goal is to annihilate enough amount of enemies before they reach the destination.