Post: #2

it's just math
an 9x9 square is 9x9=81 tiles and not 9/2=4.5 tiles

but if you want to get P values, the fastest way is the method that you already using. Since 40 tiles will be splitted into left/right and up/down, you just need to make 40/2 and this will be 20 tiles to each side, then you just need to make [center X - 20], [center Y - 20] and [center X + 20], [center Y + 20] to get all coords