Hello Math-Fun, have a look here for a clearer idea developed in the hereunder lines: https://bit.ly/2KMrmHM Best, É. --------------- Hello Math-Fun, this game (hope not old hat) is played on a Scrabble board where all squares are white, and no square has any text on it. The starting "star" square, in the center of the grid, has a 7 on it (the number, not the word, as this game is played with digits only that will form numbers – instead of letters forming words). The single player must now form prime numbers at every turn on the board – at the first turn placing the integer 1, at the second turn placing 2, then 3, then 4, then 5, etc. – this is the natural order of the positive integers as they appear (and because 7 starts the game, the player will jump from 6 to 8. No other jump will be allowed during the game). Those integers, as in the traditional game of Scrabble, must be attached to the existing structure at least by a digit (one digit per square). All visible numbers, before and after any turn, must be prime: they are read horizontally from left to right or vertically from top to bottom (again, like words in a traditional Scrabble game). Can one split the digits of a term bigger than 9 – say 10 or 11 ? Yes, as long as the split digits stay on the same line, forming one or more prime numbers within the existing structure. Example here: We start the game with 7 on the star: ....................7.................... then comes 1 and we form the prime 71; ....................71.................... then comes 2 and we form the prime 271; ...................271.................... then comes 3 and we form the prime 3271; ..................3271.................... then comes 4 and we form the prime 43271; .................43271.................... then comes 5 and we form the prime 53 (5 on top of 3 on the grid); ..................5....................... .................43271.................... (etc.) Best, É.