Played this some 3-4 years back! Remember getting headaches until I mastered it, but now I got all 155 again on my first try. Must be a skill you develop and keep forever (like knowing how to drive). Wish there were more games like this with more complexity.
You can choose the levels! No unlocking system. Replayed one of the first levels without a bandaid for around 100 times before finding out I could just skip it.
My hat to anyone who gets the impossible badge, I'm not even trying. 4 was already hard enough.