Well, it's very chaotic by design. I don't know exactly what was going on at any time, I don't necessarily understand why the bullets come back to hurt you. I do think that having some kind of level progression would help here. This way you can introduce the game's primary mechanics and the player can get a better grasp of what's going on. And after the introductions are done, then do a free play and see how long the player lasts. Other than that, that's all I have to say!