The collision detection is very buggy. I see that you changed the rendering of the unseen parts of the cube but, at what cost? lol
It could be possible that the problems that I'm having are due to my old potato (i5 2nd gen with opengl 3.3 running it in wine lol), but is also true that with the changes that you made these problems got way more common.
I made two videos with the bugs that I found:
Previous version
Notes:
1. Falling in certain position disables the resetting. *Seems fixed
2. Falling immediately and continuously makes the render buggy and you can't go up or right, going left makes you fall again. *the "buggy" rendering was an indication of a buggy collision..
3. After letting down a cube structure and having two options available, it prioritizes the undoable one. *forgot to check this one.
Actual version 0.2v
1. Never ending fall at the begging. I checked this in the previous version and it didn't occur.
2. Very buggy collision detection.
-It would be great if you add an undo button, like "Woodworm" or "Baba is you".
-It takes too much from falling to start playing.
-You went from 0 to final boss in no time omg lol, you first need to teach the player what can be done in the game.
Watch this:
I'm a big fan of puzzle games, I'm looking forward for your future progress :D