Zenge and Blue Box X and "Push".
There are 90 levels and I solved them all. The last 10 took a while.
One minor issue: sometimes the cubes didn't rotate quite right. The only thing to do was restart. This was an issue for level 10 (or so) but then I downloaded an updated version. The problem mostly went away, but not completely.
Scalak is not hard, but the graphics are really excellent.
Maciej Targoni and Michal Pawlowski have teamed up for other great puzzles including klocki.