So, I just came from finishing the game and have a lot to say.
I love how the relationship and power balance goes with the enemies. At first, it starts slow, you need to shoot them like six times in order to kill them for not too much reward. Neither of you can damage the other too effectively. With some time, you can get a few upgrades such as the first bullet damage upgrade, which immediately sets things in your favor.
However, the thing which this game accomplished which, in my opinion, is the absolute best it has to offer, is the sweet spot where the power is perfectly balanced, as all things should be. You can decide, and only you, when you want to add more enemies to the game. This creates a part of the game where you can kill enemies very easily but, if you fail to kill them fast enough, whether because you are upgrading or just distracted, there can be enough of them for it to create a horde which overwhelms you. The difficulty of the game and what makes it so much fun on this point is that no one is truly superior to the other, you or the enemies, but it is the ultimate battle of quantity versus quality.
It is truly a shame that the game goes downhill hard after that. Do not get me wrong, I really liked the game and it shows wonderful potential, but the last ten minutes of my half an hour playthrough were dreadful. The balance I commended so much on my previous paragraph is destroyed by filling the metal multiplier. The bullet damage plus the fire rate at maximum power destroy so many enemies so easily and quickly that it stops being fun after a short while. The hordes which I loved either couldn't form or, after letting them spawn because there is no other way to get them if you actively kill them, could be decimated in an instant. The healing generator, which the lack of was the main point of complain on the last game, made you nearly immortal with how little you got hit when reaching this part of the game. I forgot to mention it but, at the start, certain upgrades seem useless, such as movement or jump, but both of them become an absolute need on the sweet spot of gameplay I mentioned earlier. However, on this dreadful and slow end to it, you can just stay on the middle shooting things and just not move and you would not be in any danger whatsoever. The metal multiplier which used to be a risk that you had to take since, while it gave you more money, it also made the game more difficult is something you miss since the gameplay is way to easy and the money comes way too slow. Essentially, the last third of the game becomes a waiting nightmare on which you barely have to think while just praying that the last health upgrade comes soon and you just look at the slowly rising metal number while wishing it grew faster.
My recommendations, if you were willing to hear, would be to make the metal multiplier able to keep being upgraded, maybe just two or three more stages, making the last part of the game a very climactic battle against the hordes of enemies painting the ground, using your fully upgraded weapon to open the floor for you since it is so filled with enemies that you cannot even stand, and get much more money much quicker in order to get that last upgrade. It would not only make the game more fun, but add an actual way of dying when you are done, since I, and probably everyone else, had to kill my game character in order to end it. I understand if this would not be possible due to too many items causing lag, but if so, then why not add distinct types of enemies which make the game harder. Of course, I am no game dev but even I understand this must be a lot of work for an indie game developer, so this work is impressive for what it is.
In conclusion, I really liked the game, peaking at the middle, but it really needs some updates in order to make the last third a more fun and rewarding experience rather than a boring and slow game loop in which the difficulty is non-existent.