Engel's Enigma for iPhone/iPod touch
Engels Enigma is a circle puzzle invented by Douglas A. Engel. In terms of difficulty, the puzzle lies somewhere between the 15 Puzzle and the cube puzzle of Ernő Rubik. Like those puzzles, the goal of Engels Enigma is to first scramble the puzzle and then return it to its initially well-ordered state. Players can choose from three variations of varying difficulty.