Hey, thanks for leaving such a in depth and constructive review on our game. Since you left such a review, I assume that you also want fairly harsh constructive feedback. If you aren't open to that kind of feedback, you might not want to read the rest of this review. I am aware that you were attempting to deal with scope and perfectionism, and I will touch on that later in the review.
First of all, I'll start with what I liked. In general the game was a decently fun experience (particularly after 15+ minutes). The music was decent and the cat pixel art was pretty cute. I also appreciated the fairly unique movement option, and the stairs felt buttery smooth (I loved the spiral staircases).
However, there were some fairly major issues with the gameplay.
First of all, the movement felt pretty janky at first, and I mean for almost 15 minutes before I really got used to it. The default sensitivity of the mouse was way too high, and I didn't notice that I could change it for a while (kind of my bad). It was also fairly difficult to control the teleport feature, especially before I read the note on the itch page. Even afterwards, the teleport feature felt pretty janky, and very unlenient. I would frequently clip through walls or just barely miss a platform, and that always felt bad. One way to fix this would be some form of coyote time leniency (expand the player hitbox right after teleportation so that they can stay on ledges more easily)
Secondly, the switches and purple arrows did not feel that they significantly contributed to the fun. The puzzles that I encountered felt pretty half-baked, it was almost always "shoot at the orange thing" or "shoot at the purple thing". It would have added great depth to the gameplay if the player was supposed to analyze the switches and see if they should hit them or ignore them. (I was actually playing this way, but I kept getting killed by the rising sand, so I had to stop).
Third, the rising sand was a good idea to provide time pressure, etc. but was poorly executed. The visual warning was bad, and since most of the level was spent well ahead of it, it mostly felt like a random death event instead of a persistent threat. I would regularly get to a new section, pause to consider how to beat it, and then just die. That sucked. At the very least, there needed to be a much more clear way to see how close the sand was to you, or some sort of warning.
Most importantly, the size of the levels + lack of checkpoints was infuriating, I played for 45 minutes and literally did not reach the end of the level. The fact that every death brought you back to the beginning of a giant level exacerbated every single problem above and was what personally took the game from "kind of fun" to "oh my god, I hate this" on a regular basis. If you were attempting to make a rage game, that would make sense, and honestly would have been well executed. However, you specifically stated that you intended for the "looping" part to be replaying the level, but upside down. That does not work if a fairly skilled platformer player can't complete the first level in 45 minutes. I would have enjoyed the game much more if the level had been quite a bit shorter and I'd really gotten to experience the looping idea, which sounded quite fun.
This brings me to another point, the lack of a looping feeling. Many games that I've played (and frankly my game as well), stretch the looping theme pretty far. However, in 45 minutes in this game I really did not experience any looping, unless the main movement ability is somehow looping, or the spiral staircases count. I understand that I did not reach the looping part, but if the player being able to reach the core relation to the theme is in question, I would hope that the game would include some other looping sub-theme (I did not count having to replay parts of the level over and over again).
I have mostly talked about the gameplay, so let's talk about art. I understand the challenges of being a solo dev, and I think that we should always prioritize gameplay in a game jam. These are merely my thoughts on the art.
As you've mentioned. the art style was "brutalist". However, imagining that it had been textured, I still have a few suggestions. The mixture of billboarded pixel art sprites for the player and vines mixed with the low-poly levels/switches/arrow thingies was a bit strange. I also am not a huge fan of this style in general, but that's just my two scents. I loved the vibe of the cat, but it didn't mesh with the rest of the environement. I think making the arrows and switches throughout the level billboarded pixel art would have been a nice touch. A pixelated font would've gone a long way too.
Just a minor nitpick, but the ambient occlusion on the level looked a bit strong (much better than none though).
Nothing much to say about SFX or music, they were quite good for a solo dev.
Overall, I want to conclude by saying that this was still a really good first game for a game jam, and aside from what I mentioned above I have two pieces of advice.
1. This should have been a 2d game. The mechanics were fun in 3D but an idea like this is much easier to make fun with the precision of 2d games, and it would have been easier to make assets in the same style (though you would need a player character).
2. You mentioned how you were working on scope/perfectionism. The way I see them is almost like a tradeoff between scope and polish. In your case, I would highly suggest that you continue to minimize scope, but leave some room to really polish mechanics and/or graphics, even if it means making a much smaller game.
I didn't mean for this to just be a beat-down on the game, but I hope to provide the same level of detailed and fair feedback that you provided for our game, since you were one of the few that left truly harsh feedback.