Look at the first diagram. The middle blue piece can flip over to yellow if it moves 1 step to the left. Double tap a row or column and all its colors will flip.
There are 100 levels. The first 40 are free. After that, the rest is $1.99. I bought the level pack and discovered that there's another types of square with 4 white dots: it will affect only the orthogonal neighbors.
Must mention the ads that pop up. They appear at the top and I never noticed them. Until I tried playing this game without wifi. You cannot play this game unless you have wifi. Of course you can eliminate them for another $1.99. Truly, they were not bothersome at all.
Level 93 took forever to solve. I solved all 100 levels and according to this message, I'm prodigious.