As your first attempt, this was a solid start and I won't be unloading for all the stuff you couldn't reasonably learn in that short time period. However, one thing you should probably fix asap is the spawn position: It took me more than one attempt to even figure out what type of game this is, since I couldn't see the character and hadn't read the hints on the game page. If you started in the light, it would have been much clearer what to expect and how to approach it.
Other than that, I agree with KrNo and SeeOne: Make the bullets pierce through, since the beam isnt't stopped. In fact, I wasn't sure until the end, whether I was possibly hitting more than one enemy (since they are quite bullet-spongy) and there AI acts in such a way that having a piercing ray weapon would allow for great crowd control by lining them up and dispatching them. Also lower their movement speed just a little bit, add WASD for movement input and you will have a tremendous improvement.