Mahjong Free is a tile-based matching game. Despite the name, Mahjong Free is not the traditional mah-jongg game you'll see played with four players, but what's called Mahjong Solitaire, in which you try to match identical tiles. Mahjong Free is available for Mac and iOS devices.
Mahjong Free starts with a stack of tiles laid out in a predictable pattern. The goal of the game is to choose pairs of identical tiles, which are then removed to show tiles underneath. To finish the game you've got to choose the pairs in such a way that you can completely remove all tile pairs, instead of ending up blocked and unable to move. The choice of which tiles to match (there are typically four of each type) to open up other matching possibilities is where the strategy comes into play. Mahjong Free gives you traditional Chinese tile faces but you can choose from several backgrounds. There's a hint mechanism if you want to learn the game a bit better.
We've played Mahjong Free for many months, and as a Mahjong Solitaire implementation it is very well done. Like many people do, we originally got the game thinking it was traditional mah-jongg, but the implementation of solitaire is done well enough to keep this game on the regular playing list.