I have cleared the game. I'd like to write down some of my thoughts.
First of all, there is almost no feedbag for the fact that the gunshot hit the target. This should have been represented by some kind of effect, which would have had a significant impact on the playfeel.
The sound of the flamethrower was very intense and continuous, at least when played on a mac. I think some of the sound effect assets represent the flamethrower. The flamethrower is a pretty strong and fun weapon, but the sound is quite distracting.
Having a variety of weapons and enemies is a good thing, but I didn't think it was well integrated into the gameplay.
A great example of this type of game is "Serious Sam". In that game, the player has to use different weapons for different types of enemies.
On a related note, the game was monotonous overall. Especially after Wave 20, I felt that the game was just repeating the exact same levels over and over again.
But is this monotony something that can be solved by adding more weapons and enemy types?
I don't think so. The variety of weapons and enemies in Serious Sam is similar to that of this game, but I rarely found it monotonous to play.
The reason for this is that each level gives the player a completely different playfeel, depending on the combination of enemies and the type of gun you are carrying.
It's a long story, but overall I enjoyed this game. Good job!