The location of the bonuses on your screen
The bonuses appear at the bottom of your screen when you do a puzzle. When you earn Reveal, it appears at the bottom of your screen in the middle. When you earn Magnet, Reveal is on the left and Magnet on the right. Finally, when you have earned all buttons, Reveal is on the left, Magnet in the center, and Hammer on the right.
Each button is a gauge: it is progressively filled with color and when it is completely colored, you can use it.
For the Hammer, if you place two pieces in the right place but you make a mistake on the third, the gauge resets. You must put three new pieces in the right place in a row to be able to use the bonus. However, when you use the Magnet, it is considered as a correct move and the Hammer Gauge is filled up.