Let's maybe start from the visuals. I really love those pixelated graphics that appear in this game, with the combination of red-black color palette, where the only differently colored object are the main player, and the treasures you can pickup. The graphics are pretty unique, seem as a whole, and probably are the best part about this game!

Sound effects are okay, but I do have a problem with the music. Now, I do appreciate that you made your own soundtrack for this game, and not just one or two tracks, however, the music isn't particularly good. It's repetitive, after a while gets very annoying, and just seems like something you'd make in Bosca Ceoil on your first time using it.

The gameplay itself, I would consider very fun, if not for one, major issue, but let's not get ahead of ourselves. Controls feel responsive and smooth, and the addition of air jump is a good one! The levels themselves, are also not bad. At first they might be a bit hard, but after a few tries, they usually are very easy to beat, and completing them without taking any damage, does feel very satisfying. The only minor issue with the gameplay are physics, which sometimes might not work correctly, leading to such results as sticking to the floor, and being pushed back when standing next to turrets and other sprites.

And now, let's talk about this major issue with the gameplay. That issue being, restarting from the first level, after every death. I know, you wanted to create a difficult game, but that just doesn't work! Needing to spent a few minutes after a death that sometimes might be accidental, just to repeat 10 levels you've already played tens of times before, isn't challenging, but rather frustrating and dull! And the solution was very simple: just add checkpoints! Maybe not for every level, but rather for every 5 levels, and then the game would have been much better!

That one issue, completely ruined the experience for me. Which is a real downer, because besides that (and maybe the music) the game is good! But for now, I consider this game slightly above average, it definitely needs some more development and polishing.

I made it to the first inverted level on a timer, with the big machine guns. I fell, again. Then I couldn't go back there and ended up rage quitting, because I've spent too much time on it.

One major piece of advice: push players to the shop

The first time I did the first level with turrets, I solved it accidentally, and then I couldn't figure out how, and almost quit the game altogether. I later realized that I had solved it by jumping while in the air, which is also very much non-obvious. That's a really neat mechanic though, so you should probably add some text explaining it. Even during the jam's voting period, you're free to edit the itch page, so add something there that explains how to play in a less frustrating way! It's a great game and I'm afraid you'll turn away many players who won't understand how to progress.

Gameplay

Perfect. The controls feel smooth, even with the orange cube it feels super natural to control it (I usually struggle with fast-paced characters) and I was able to make precise jumps pretty easily. Only issue was sometimes after a high jump it feels like you get stuck in the ground, and this can mess up some jumps.

Graphics

The art is really neat, but more feedback on some elements would be appreciated, notably mines (I initially thought they were buttons and didn't understand why pressing a button would restart the game). Camera movement could also use some work in the larger levels, maybe move it in the direction of the player's movement on the X axis so we can see further, and increase its drag on the Y axis so jumping with 4th cube doesn't get nauseous :p

Audio

Again really good, as others mentioned the soundtrack restarting on death is quite annoying at the start. Some feedback would also be appreciated on damage / coins / level finish, especially when the key disappears and nothing happens and you wonder if it's bugged - maybe a popping sound from wherever the key spawned?

Innovation

Platformers aren't new. But this one is particularly vicious, and I kinda like that, so you get 4 stars even if I hated loving it :)

Theme interpretation

I feel like you've added "Bounds" in the title just to earn my 5th star. It worked.

Very smooth control and highly polished art and sound! You really made a platform game who has many little tricks! Just too hard to even beat half of them D:

The graphics look polished and fun!

Movement feels nice, quick and responsive. Except that there's something off (I can't put my finger on it) that makes certain jumps a little imprecise and sometimes too difficult ... could just be my lack of skill.

I also second feedback already made:

• The music becomes a bit annoying with many restarts. If you can't solve that, maybe a slightly different soundtrack could soften this issue? Or creating 3 slightly different soundtracks, playing one randomly on a restart?
• I understand your decision not to use checkpoints - it surely makes the
  game harder and more tense. At the same time, it just made me quit after failing for the nth time halfway through. In general, I've noticed players want to be able to retry a challenge as quickly as possible, instead of redoing something that's not challenging anymore for a few minutes (every time). For me, personally, the game is hard enough as it is :p
• On some levels, you can't look ahead far enough, which means you're basically jumping blind the first few times you enter the level. (After that, you have somewhat memorized it and can navigate.) This would be fine ... if the game had checkpoints.
• Feedback on damage (like an animation where the player quickly displays a red color, or something) would also be really helpful.

All in all, great graphics, great controls, solid core game mechanic, and you're able to create a really fun atmosphere where you just want to retry until you succeed! 

The graphics are adorable and the music is a nice touch.  I quite enjoyed the gameplay as well. The only thing I would like to recommend is making the platforms more visible in certain levels (I think it was level four?)

I liked the art style, but the way you stick to the environment when jumping made things feel a little less than precise. I would also recommend having the music play continually, rather than restarting every death, or at the start of a new level, as it can get grating. Otherwise, nice entry!

I liked the graphics and the general style, very clean and effective.

The challenge was fun and it was satisfying too learn the levels as you get further between every death.

The only thing i would like to change is the parts where you can't se the next platform before you jump.

Need more checkpoints. And more obvious indication when you take damage - I was thinking spikes do nothing.