Simple shooter that was surprisingly enjoyable to play. Especially impressed of the "challenge" at the end. Many aspects of the game are on par with commercial games, especially the satisfying shooting mechanics and animations.
Could use better lighting at times. Some bits are not quite refined, for example there is no incentive to use the pistol after you get a better weapon. Spawns are harsh and you can lose all your lives in a quick succession. Ridiculously difficult above normal difficulty but probably doable.
Try it out, challenging shooter fun and you will enjoy yourself for the 20-30mins.