+ & - : A Zen game

This is a special game, a bit Zen a bit strategic, take your time but not too much. The rules are two: 1) equal numbers on background of equal color are added 2) different numbers on background of different color are subtracted Tap two numbers, the result will take the place of the second. Make the highest score you can. - you can save the current game and start a new one, so that you can play up to 9 games at the same time. - when you exceed 500 points, you'll be able to swap the numbers of two quartets of different color, dragging one over the other. - customize the colors of the board with 351 different combinations - you can also change the user interface color, light or dark