Good job on your first game!
- I had a couple of issues, the fire rate was pretty slow and especially on level 2 it felt pretty impossible to shoot all of the enemies, it'd be nice to see how long it takes for you to reload.
- The difficulty curve could also be a little better, most levels were pretty easy and the same but level 2 was really hard.
- On some levels the path of the enemy was a little unclear, so it would be nice to show a path like you had in the other levels to see how long it'll take for the enemies to reach the end.
- I think the pause menu in the beginning should probably be a start menu, maybe you could explain some stuff in the beginning as well like what the evolution speed is.
- In level 4 the gun shot over my crosshair, and the timer ran out with no ending.
- The third level only had one enemy for me.
- The theme was a little unclear, you do change guns between each level but they seemed to be pretty much the same, the variation in sounds and sprites is nice though.
Aside from that, I think you did a pretty good job on your first game, especially in such a short time frame!