Really good balance of difficulty

Just coming to the end of Quell Reflect (having finished Quell) and thought I'd drop a word of praise. I thought the balance was really good -- some early levels were "obvious" so you didn't get discouraged; several levels, with a bit of "forethought" had only one "viable" way of solving (but sometimes finding the shortcut to get a perfect score kept you on your toes). Very few levels (e.g. "Sorry") forced you into almost random exploration.

More please!