Slide the cards up, down, left or right across the grid. When cards bump into other cards, they will stack as long as they obey these two simple rules -- no stack can contain more than 4 cards, and no stack can have a value of over 21. Easy!

Slide the cards, making stacks, with the goal of building stacks totaling 21. When you make a stack of 21, it is moved to the score pile, leaving room for more stacks. When you build a stack of four cards that is less than 21, it's moved to the discard pile, to be used later. You can use this to your advantage.

The game is easy to learn, but once you start playing, you'll find subtle tactics and methods you didn't think of at first.

Can you get the ultimate achievements?

How many TwentyOnes can you make in a single game?

Download this App and find out.