Four simple steps to play a trick on you friend:
1. Choose a horrifying picture.
2. Choose a terrifying sound.
3. Set the time after which you want to scare your friend.
4. Start the game.
Give your telephone to your friend in order to let him play the game. After the set time, the horrifying picture with the terrifying sound will startle your friend :).

It's a prank app.

Have FUN!