Sigmatres is a number game, the goal is to open all closed cells, you have to equalize Current counter with Target, once Current and Target are equal the Target value will be added to your total score and the matrix will get regenerated with new numbers.
In level 3×3 each time you add 200 to the total score a cell gets opened, and in the level 4×4 a cell gets opened when you add 350 to the total score.
Only blue and red cells can be changed, blue cells can be set to 2, 4 or 8, red cells can be set to 3, 6 or 9.