1. Some hexagons have 2 colors. The orientation matters.
2. Some hexagons have 2 colors where the orientation does not matter (harder).
3. Some hexagons, which have 2 colors, rotate after each swap. These are the most interesting.
4. Some hexagons are fixed in place and cannot be swapped.
There are 90 levels altogether. I've done 84.
There's huge potential for many more levels with many more pieces.
http://www.andrewjadams.com/game-dev/hand-crafted-puzzles-how-and-why/ Definitely read this piece where Adam describes creating his puzzles.