Each boss has it's own weakness. If you stand in one spot and dodge the bullets there, you can beat it pretty quickly. Also the more money upgrade is nice investment for later in the game.
This game is great for its originality and innovative idea. This game is both fun and has a easy difficulty for you to see his idea of a game. Though, you should be able to rotate your weapons and other features could be added. This game demonstrates that original ideas still exist and some ideas haven't been done yet.