Battle Box

1. Each player will take turns placing a number in a 5x5 grid to take ownership of a square.
2. For each non-diagonal adjacent square to the placed number, an opposing square will have the difference between it and the placed number subtracted from its value; an allied square's value will gain a bonus of +1 (max 9).
3. A square reduced to below zero will be reopened.
4. The game is over when there are no squares left open in the grid.
5. The winner is the player with the most number of squares under their control.