The game isn't that short for sure, I kept going on because I hadn't even realised that progress was saved, just left the tower (without doing the thing with the button and the door) and reached the hazel trees before going to bed.
The game is fun, I downloaded it based on the "hopefully challenging" mention and wasn't disappointed, I can't say I won't hit a wall with my poor skill but it would be perfectly fine and the sequences so far have been satisfying to beat.