You will be given a random number at the start of the game.
There are four crystals below. By clicking on a crystal you will add a specific amount of points to your crystal score.
You win the game by matching your total score to the random number, you lose the game if your total score goes above the random number.
The value of each crystal is hidden from you until you click on it.
Each time the game starts, the hidden value of the crystals and the target score changes.