A Top down shooter! I am very bad playing at those, so I couldn't survive long :D.
It was fun, and well made. I didn't find any bug. The city background is good. The only thing I would change is that the yellow circle of the player is a bit distracting, and the spiders (in contrast) are a little hard to see. I didn't hear any music or sound effects in the game, but I hear them in the video...
Even so, a very fine entry, and a game fun to play. You can expand it on different scenarios for each wave, for example. Good work!