Cool game! although, adding a background would be a nice touch :)

The sound design was good, especially the one when the enemy dies :P

The game could use a bit of polishing but overall, good work! 

If you are starting in the world of gamedev let me tell you that this is a nice first step, trying to make something out of nothing is always hard, and if you're using an unknown tool is even harder. I always like to track novice devs and see their evolution, give advice and more ^^

about the game itself: It can be improved, the second level is very unoptimized, probably because there are so many enemies there at the same time. the graphics could be also improved but the idea behind them is quite original. I've died a couple of times without knowing why, but the detail of putting there so many retry buttons made me smile XD
please keep doing game jams!

If you add some random map generation, wepons and AI - this will be gold