Nice game! I did enjoy the movement and overall gameplay loop.
Unfortunately, there seem to be quite a few bugs still in the game. I could go into negative ammo (I was clicking quite rapidly, so maybe that's the issue?), the game over message didn't disappear for me on restarting and twice I got stuck in a wall.
Example of the two most visible bugs. (Also, the game began lagging a bit here, probably because enemies spawn in infinitely? That could mean it can cause issues if they get stuck on a wall like this. Limiting the amount of enemies that spawn at the same time should probably help!)
But those things are something that can easily happen with a time limit like this. The overall game is enjoyable, excited to see where this goes if things like the shop are coming!