There are 16 pieces of a picture left unorganized, you will organize the pieces in the right way.
Though I am saying that there are 16 pieces, actually there are 15 pieces of the picture and 1 piece is the free space. You can move a piece of the picture in the place of the free space only when the free space is adjacent to that piece.
By doing this as many times as you need, finally you will have arrange them in the right order. The original is also given so that you can have clear concept about the goal.
That's all. To move a piece of the picture to its adjacent free space - just click on the piece.
I hope that you will like it.