Four By 21 is a free Android game developed by Words and Maps that combines solitaire and blackjack. The game is played in single-player mode, where you are dealt one card at a time and have to choose one of the four stacks to place the card. The objective is to clear each stack by adding up the card values to exactly 21. If the value exceeds 21, the stack is busted. The game ends when you bust 5 times or run out of time on the clock.

The game is fast-paced, and bonus points are given for clearing consecutive stacks. The graphics are clean and straightforward, and the game is easy to play, making it a perfect time killer. Four By 21 is brought to you by the makers of Pressed For Words, and it is a great addition to their gaming collection. Overall, the game is enjoyable, challenging, and engaging, perfect for anyone who loves solitaire or blackjack.