1. The board has a 10x10 matrix with 100 tiles colored blue or green. Blue tiles has a number (1 to 9) on it. Green tiles do not have any number on it.
2. Any blue tile can be moved to any other blue immediately above, below, left or right provided the number on destination tile is greater than or equal to the number on source tile. Eg - A blue tile with 3 on it can be moved to a blue tile to its immediate right with 5 on it, but a blue tile with 7 on it cannot be moved to a blue tile immediately above with 4 on it.
3. Any blue color tile cannot be moved to a blue tile that is immediately diagonal to it. Similarly any blue tile cannot be moved to any tile that is left, right, above or below it but not immediately. Any green tile cannot be moved. Any blue tile cannot be moved to any green tile.
4. When any lower numbered blue tile is moved to any equal or higher numbered blue tile, the number on source tile gets set to 0 and color of tile changes to light blue. The number on destination tile gets set to unit digit of a number which is sum of source & destination tile. Eg - If 3 is moved to 5, the number is set to 8. If 7 is moved to 8, the number is set to 5 (unit digit of 15 = 7 + 8). If the number on destination tile is set to 0, its color changes to light blue. Eg - If 5 is moved to 5, both source and destination tiles are set to 0, and color of both tiles change to light blue. Light blue tiles cannot be moved to any other tile.
5. Any blue color tile that does not have blue color tile immediately left, right, above or below cannot be moved. The color of such tiles are changed to red. Red tiles cannot be moved.
6. The aim of the game is to successively merge lower numbered blue tiles into equal numbered or higher numbered blue tiles. The game ends when all the blue tiles are converted to light blue or red tiles with no blue tile left on board. Fewer the number of red tiles on board, higher will be the score.