As you can see there are 12 balls. After all, that's what the puzzle is called!

One of the balls is either heavier or lighter than the rest.

You have 3 weighings to decide which one and whether it is heavy or light.

You can arrange the balls however you like.

Click on a ball to pick it up then click where you want to drop it.

Place a ball above a pan to drop it on the pan but note that each pan can hold at most 4 balls.

Click the button on the scales to activate a weighing.

You can check your answer by clicking on the title. The faulty ball will be coloured green for light or red for heavy.