Left-click on the mouse to select/unselect cards. Press [space] to play cards after the selection is complete.
Players can play cards that have the same suit/rank with the face-up card in the middle. Players may choose to play additional cards that have the same rank in hand (need to select the first card that can be played, though).
The winner is the first one to run out of cards in hand. :>
Cards Art attribution:
Byron Knoll: http://code.google.com/p/vector-playing-cards/
https://opengameart.org/content/colorful-poker-card-back