This was quite nice! I especially love the way that the 3D perspective is used here. There's a lot of fun little objects in the environment, and things hanging above your head, and this is a really cozy aesthetic touch that I haven't seen much before, and it adds a lot to the atmosphere of the game.
I had a lot of fun trying to move really fast through certain puzzles. The player movement has that sort of snake-game feel, where you can easily overshoot the square you're trying to end up on by one. So, it's satisfying to correctly execute tight turns and the like.
I found that the death mechanics were a little glitchy. In particular, I played this game to various stages of completion approximately 3 times. Every single time, my cube eventually ended up rotated abnormally--it seems like the transform is somehow not getting reset when it dies? And, in my first playthrough, the cube eventually turned completely invisible (presumable the scale got permanently set to 0 somehow), and I decided to restart the game at that point, as it became much harder. Also, when respawning, the cube would end up moving really fast and going through walls--although this only seemed to occur after dying several times. I think this bug should be reproducible just by holding down the arrow keys immediately after respawning--it seems like the cube sort of glitches through walls and then dies (because you usually hit lava very quickly while this behavior is occurring).
Despite these bugs, I enjoyed all the gameplay. I found the maze puzzle at the end genuinely took a while to figure out, as there were a lot of little factors, like which walls you could and could not move through. I also liked the way that the world was one continuous space; I think this contribute to the atmosphere as well. Overall, great little puzzle game!
Oh, one note: I did play with the Windows version, although I also tried the web version after my guy turned invisible, but ran into the same rotating-bug. All that is to say: the Windows version seemed to work fine for me!