I played it the 2nd time now. The first time I did not like. It was because I played in usual itch window. With a small window you can not get enough speed to make some of the levels (like breaking the ice wall was impossible), since you can not draw the mouse far enough.
On fullscreen it works well and looks also better. It's same problem as DeltaVs game. Better write it big on the game page, to best play it in fullscreen.