There are some great bones here, and it's impressive how much you were able to get done in the 48-hour period! That being said, there's a lot of room for improvement too. My biggest complaint is that there's a lot of "hurry up and wait" gameplay mechanics, which don't feel great. There's also not a ton of room for strategic planning, since wave composition isn't known ahead of time and seems pretty sporadic.
I don't want to come off as overly critical though. The basic concept here is creative and interesting, and with a bit of polish, it could be a really great experience!