Interesting idea! I really like this kind of approach for a game like this. However, I feel it would have been better either without a time limit or with a bit more time. Also, the fixed camera angles make it hard to aim at enemies, sometimes it's more convenient to just wait for them to come closer so you can get a better shot.
That said, it's really well done, especially considering it was made by a single person. With some improvements to those aspects and more variety, it could become a very interesting game as a final product.