This is a really cool concept and I liked the aesthetics a lot. With some more time, you could really use the aesthetics to enhance the theme, as it has a lot of potential already. I liked the arcade nature, and your game is one of the only ones that has a reason to play it multiple times (and the menus to accomplish this easily).
The game does require some tuning, though. The mouse controls were way too sensitive, the collision was a bit off (which is understandable), and I didn't really find a use for the firing at all. The mouse didn't get locked in the web player, so there was a limit on how far I was able to travel up or down. Also an ability to invert the Y axis would be nice.
Overall, incredible job. Congratulations.