Mahjong Unlimited is a very nice computer version of this board game. In Mahjong, you have to remove pairs of pieces from the board to clear it out completely. You can only make pairs with pieces that are not blocked by others above or on the sides. Unlike similar Mahjong games, this one generates puzzles and the developers guarantee that they can all be solved. This doesn't mean that you will be able to solve them all. To do that, you have to pick the right pairs to clear from the board at the right times. I always try to free the ones at the center of the board, so I have more options sooner during the game. There are lots of different strategies, though.
The game board and all the pieces have a nice design. When you start playing, a timer will start running. And your game statistics will be kept by the application to adjust to your skill level for future games. This adaptive capability ensures that you won't get bored easily and that the game is challenging to you. I haven't played enough games to attest to how well the application adjusts to my skill, though.
Unlike its iOS versions, Mahjong Unlimited does not let you play against other people, which is a feature that I would love the application to have.