Thanks for the detailed feedback! Haven't heard about peglin, I'll check it out.
Yes, the game still needs a lot of polish, especially with the UI.
Sticking pieces to the side of the board only happens with one specific enemy with the magnet skill. I guess there also is one upgrade for the warrior that lets you rotate pieces even when there's no room. At first I thought it would be really strong but it can sometimes screw you over if you rotate something right next to the end of the screen so it's probably going to get scrapped or at least changed in the future.
Z and space are both for the ninja character and for some upgrades/blessings. Should be explained better in the future.