The game has a pretty unique idea here, but I think some of the restrictions/executions hurt the exploration of said idea. The small screeen and the tighly packed enemies mean that going between the enemies and manouvering around is hard to do, and quite risky to your life, while the optimal play is to go on top/bottom/left edge and still press that direction to shoot the exhaust into the middle area, until eventually you finish them on the left side.
Graphics and sounds are nice (altought the bomb/lighning effect is a tad loud), pickups are a nice mixup, but I think they suffer from the same thing mentioned above.
Overall nice idea and execution, which (to me) suffers from the screen resolution being so low and the enemies spawning in tightly knit groups.