Triple Town by Spry Fox started out on the Kindle, but I first noticed it on Facebook and subsequently on Google+, one of the first game on that platform. Most recently it has been released for iOS devices.
The gameplay is an innovative take on the match three mechanism. Objects (grass, bushes, trees, cottage) are placed on the playing area to form groups of three or more matching objects. But instead of simply disappearing as they match they are replaced by the next object in the sequence. Three grasses become a bush for example.
This bush can then match two other other bushes and be replaced by the next higher object, a tree. And so-on, through houses, mansions and castles up to the ultimate in Triple Town architecture, a floating triple castle. This makes the game very strategic, much like Chess or Reversi, as the placement of objects can become important dozens or even hundreds of turns later.
If that were all there was too it the game would be interesting enough, but an extra level of strategy is added by 'bears' which once placed can move if not blocked. They can, and often do, obstruct anything you are trying to do. The can be killed by trapping them so they cannot move, and turn into gravestones, which can be matched with other gravestones to make churches, cathedrals and treasure chests.
After a short while ninja bears appear which can teleport to any free square so cannot be blocked. These can be killed if there are no free squares or by an Imperial Bot which can also kill regular bears or remove any object on the board. Finally there are crystals that can match any object, especially useful for matching higher level objects (houses and above) that don't appear.
The thing that really distinguishes the game is the visual design. All elements are distinct and recognisable, with the progression of higher value objects matching the complexity of their design. They fit into a deceptively simple design where they are the building blocks of a town. The game mechanics stop you loosing your inner city planner on the design of your town but the pieces fit together so well they almost by accident keep forming patterns and designs that look like a working town.
This is helped by the small characters that come out of the buildings, strolling chatting, and even picking apples off trees, and the subtle but effective sound effects. The overall effect is of a living, breathing town or city which keeps running as you play your game. These elements are almost irrelevant to the gameplay, but lift it above other games that just sit there waiting for you to make your move.
On Facebook and Google+ it is a free app, monetized through in-game sales. As with other games it has a free currency, coins, and a premium currency, crystals, with which you can buy extra moves, objects when you need them (normally they drop randomly), and some special objects to help the game.
The weakest element is perhaps the store. There are only so many items you can buy for each town, and it's not unusual to run out of things to buy long before the town is finished, and so have money but nothing to spend it on (except extra moves although I prefer to wait for them to build up over time).
Another limitation of the game is it does not change. Over time as you play and get better you find your towns and cities last longer, and so earn higher scores. But the game mechanics don't change and there's little progression apart from this. Finally the social elements are pretty weak for a Facebook game: there's not the same incentive to recruit friends as in a game from Zynga or one of the other social game specialists.
Perhaps the biggest sign of its originality is that it has been unashamedly copied by other game makers a number of times since its release. None though of the other games have the same quality or attention to detail. My own interest is that more than any other recent game it has informed the design of my current game, although the influence is buried very deep.