I really liked it. It's simple, but it hooks you effectively since you're constantly facing hordes of enemies. One detail I really appreciated is the idea of having health and ammo share the same resource. This adds an interesting strategic layer, as managing both becomes essential for survival.
I also liked that, as the game progresses, the new enemies forced me to rethink my strategies. This shift in difficulty and the need to adapt adds a good level of challenge.
One downside is that, at the beginning, the game can be frustrating if you run out of ammo. In these moments, the only thing you can do is wait to get killed. A possible solution could be to add a mechanic where, if you run out of ammo and there aren't enough in the scene, they randomly drop so you can collect them with the vacuum. This would allow you to keep playing without getting stuck due to a lack of ammo.
That said, it's a very well-done game, especially considering it's part of a game jam. It has a solid, dynamic, and challenging design. It's easy to get hooked. Great job!