I'd like to clarify my thoughts on level 4 since reading the comments that seems to be a point of contention from other players as well.
The game teaches quite well to use your body as a physics object and terrain to platform on and swing about. It also teaches you to throw yourself at sawblades until the buttons are pressed and objects removed.
So in level 4, when the player is introduced to the turrets, it feels frustrating that the physics object and terrain solution is shut down by the pistons, however the level does use the 2nd approach taught to the player and the theme of the game jam. Death is an opportunity, and every time you run into line of fire, the turrets lose ammo, and if you keep running in, you will progress.
On top of this, when we get to later levels with turrets, the creative solution most wanted to work in level 4 is rewarded, effectively making the player tackle the same problem in two different ways. I don't think level 4 is too difficult. Death is part of the solution not a punishment ,but the player doesn't feel rewarded or like they're making progress until the first turret goes down, and they may not understand why.
I want it to be understood that I actually enjoy this level, me and a friend each worked to get 0 deaths on this level, but a more clear ammo reserve on the machine guns being depleted may help players understand their goal more.