Navigate a grid by keyboard

I am working to make a game accessible. I am using battleship game as the basis. I can navigate by tab key but only from left to right and down. When I go away from the slide and come back, it always starts at the beginning.

I think the NVDA speech reader will allow the person to navigate with arrow keys. What can be done for the sighted person who lacks mobility so they have to use a keyboard?

I cannot find any trigger commands to allow the player to move in any direction with a keyboard only. 

Any ideas?