Clear the screen on 250 levels. 15 different square types will make this process really interesting, especially as they are combined in a lot of unique ways.
Unlike other puzzle games there is no way to lose or get stuck, you don't have to restart levels, yet you'll have to use your brain to find each new move.
The progress on every level is constant - get rid of squares one by one, and you will find the solution. If you feel stuck - use a hint, skip the level, or close the game and continue later from the same place.
There is no tutorial in the game. You are smart enough to understand everything yourself, and it's also a big part of the fun.