We understood too late that this small tutorial isn't enough, and placing text to explain wasn't a good solution, we really need to work more on actually teaching mechanic. Thank you for playing 
P.S. When you shoot and hit an enemy with the last bullet of an ammo type, all empty ammo is reloaded.

Thank you for comment ). Doing things in the last second was part of the plan to make puzzles more mechanically difficult, so you would need to come up with plan and then execute it, but fair point. 

Yep, you were cleaning, with the cart, with you *half dead* body, with ammo.  Doesn't really make sense but is a punishment that boss gives you after you lose to him. 
Frustration: we were doing levels in the last day, so have not had time to test the properly, and do a lot of them, so we end up dark soulsing them, so player can learn what he doing from trying. Maybe was better to just turn down difficulty

Restart button would give player incentive to give up early, you can work you self out from different situations if you understood mechanic, and more level is complex more different ways you can pass it (we find part of them after posting xD).  So its a trade, but probably restart button would be good addition in this way: cart is speeding up 10 times while you press it, can also help skip waiting time if it isnt you 1st time on the level.
Recharge happens when you hit with last bullet in the ammo, and this is almost whole game idea, so i probably could add abilities, that let you recharge or delete all enemies, but this will ruin puzzle element or just end up mandatory to past puzzles. More ammunition can give more room for mistake, but puzzles are design around 3 ammo, so 4 can actually make them a lot more difficult.