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 a Reveal, it appears at the bottom of your screen in the middle. When you earn a Magnet, the Reveal icon is on the left and the Magnet icon is on the right. Finally, when you have earned all buttons, the Reveal icon is on the left, the Magnet icon is in the center, and the Hammer icon is 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.