Overall, I really liked it; a very odd and unique movement mechanic. I think the core skeletal of the game is strong, it just needs some tightening up, especially in terms of teaching the player. I feel with explanatory mechanics like the signs from the first level (which should be improved to be re-readable and optional and not halt your progress against your will), and with improved level design, the player can be taught each new mechanic more slowly and deliberately. Signs like that are a crutch, but crutches are not inherently bad, sometimes necessary.
Puzzles games are tough and I commend your effort. The ideal with a puzzle game is to make the game not too difficult so as to be frustrating, but still make the player feel smart. I would recommend breaking down the level design for Portal Portal 2, Braid, and Baba Is You; see how they slowly introduce new mechanics bit-by-bit so the player can follow along. Portal is 70% tutorial but it doesn't feel that way. Baba Is You (I think) is a bit harder than the previous three, but there's a lot to learned there. I actually think Transilio has a lot more in common with a sokoban puzzle game than with a more typical puzzle-platformer. The clunky, chunky, grid-based movement and resultant level design is much more reminiscent of a sokoban puzzle game to me. It's like a sidescroller sokoban game to me, and I think that's really cool and interesting. There are great lessons to be learned and copied from previous sokoban games, such as the inclusion of an undo/redo system, which I think this game is screaming for.
Conveyance needs improvement all-around, which is a totally normal problem, especially for puzzle games. As game creators, we know exactly how the mechanics work and how to play the games, but that isn't true for our players. It's difficult to impossible to get in the mindset of a player totally new to our games and see their perceptions; that's why playtesting is so important. Online playtesting is great, but I encourage you to do some in-person playtesting as much as you can with friends, family, and strangers if you can wrangle them. The trick with playtesting is just to hand them the game and say nothing. Don't explain anything about the game, particularly the controls and mechanics, as the game should be teaching those by itself intrinsically. When you have a doe-eyed player seeing it for the first time, those fail points of conveyance become obvious. Again, I'm not disparaging y'all, this is a completely uber-common and normal part of development, we all have to do it, especially for puzzle games.
The presentation was pretty good, I liked the art and music just fine, though they didn't blow me away if I'm frank. I really liked the neat little low-tone background pattern with the square dots and boxes. That was rather lovely. The rest of the art is fine; could use some more juice, a bit more energy and bounce with animation perhaps, or some procedural spice with particle effects. The art for the mechanics might be changed to become a bit more clear to the player what's happening, explain the mechanics better intrinsically as I discuss in the video.
You did a wonderful job with the itch page here; great use of color, background image, semi-transparent background 2, explanatory text, logo, and screenshots. This is a pretty 100% itch page with everything included, which is a big deal! Your game pages are really important and you did a lovely job. The only additions I could say would be: marking everyone as a contributor as the game so you all show up as authors for the project, which Bricks already did after we discussed this in Discord; listing the credits on the itch page text itself, not just in-game; and setting a video for the game, but that's low-priority. The fact the game is playable in-browser is hugely important; that lowers the barrier-to-play tremendously, so everything else marketing the game matters much less. If this was a downloadable game-only, then I would say that a video is much more necessary, but here you're all good.
Awesome job to everyone who worked on the project; I look forward to seeing your progress on this game and future projects! Cheers!
-Sincerely, Gunnar Clovis