Click on the right button at the bottom and the tiles of one row and one column will change color.

Now click on the tile located at the intersection of this row and column. The playing field will return to its original state.

Move the slider a little to the right, so that the number 2 appears to the left of it and click on the right bottom button again. Now two rows and two columns on the playing field have changed their color. Think about which two tiles you should click to return the playing field to its original state.

If you have difficulty doing this, double-click on the left button at the bottom to see a hint. You will need to click on the tiles that have black numbers.

By changing the position of the slider, you can change the difficulty of the game within a wide range.