See if you can get through to the end of the level. In order to complete the level you have to get at least seven out of a total of ten stars. But, it won't be as simple as that sounds. You have to avoid the walls and other enemies while you do it. As a secondary goal, you have to get all the money you can. To do this, grab the squares in the level. The money is needed for upgrades. Move around with the arrow keys, fire your weapon with the space bar and change weapons with the number keys '1-3'. Good luck and have fun!