Hey, just played your game. I think it's a good start but it's definitely lacking some core elements. For example, there doesn't seem to be any sort of win condition - and that's not necessarily a bad thing but there's also no way of tracking your progress. Whether it be a timer, a kill count, or a scoring system I think there needs to be something to encourage you to keep playing. Visually there could definitely be more going on, at least with the background. Right now its just a solid gray background. Even adding in a couple repeating tiled textures would go a long way toward improving the look. The audio, while not bad, does get old quickly. I think a longer music track would have been a better choice as it repeats quite often. Also you should really consider adding in some sound effects both when the player shoots and when the virus gets hit/dies. I hope you're able to implement some of these changes, just a few small additions will really go a long way toward improving it.