* 900+ levels.
* TIME TRIAL mode to play with your friends.
* vivid sound effects.
The history of this puzzle is quite interesting and similar puzzles were first printed by Sam Lloyd in the Brooklyn Daily Eagle (1897) and in a 1932 book titled "Puzzles and Curious Problems" by Henry Ernest Dudeney. More recently, this puzzle was popularized by Japanese puzzle game company Nikoli under the name Arukone.