You need to have enough "free space" to move a stack. The number of free spaces you have is computed using the number of free cells in the upper left corner and the number of free stacks in the lower part of the board.
The formula is X = (F+1 ) * (C+1)
where X is the maximum size of the stack you can move, F is the number of free cells and X is the number of free columns.
I have to review the code. It's the first version of the game. It's a little bit buggy.
Thanks for playing it
