Java can be used to create a complete graphic user interface that can be used to interact with the user.
There are 14 pairs of cards arranged randomly and turned face down. The aim of the game is to pair them all off, but you can only turn over two cards at a time. You have twenty tries.
To turn over a pair of cards, click on each of the card backs. To select another pair, again click on the card backs. If the previous cards were not matched they will turn over again automatically. If they were matched they will stay face up. You have won when all the cards are face up.
You can increase the difficulty level of the game by moving the slider to the right, but you will have to start a new game for the new settings to take effect.