Beat all 24 levels. At first the control is a bit counter-intuitive, but it is not difficult once I am used to it.

The concepts and the levels are interesting. New obstacles are introduced at a nice pace. I particularly like that the box has multiple functions. For the levels, they have enough variety, which is nice. Some levels are too vast in my opinion, but it is not a big deal. Lv22 is a bit tricky for using a technique that is never explicitly taught (I did feel elated when I figured out the solution). Lv24 is a nice closing level too.