I would second this. I just thought my 5 year old cousin grids and locations on a grid simply because I wanted him to play battleship. Next up: difference in

I would second this. I just thought my 5 year old cousin grids and locations on a grid simply because I wanted him to play battleship. Next up: difference in distance between one battleship to another; difference in distance across two axis; difference in x and y being called slope. Then the possibilities are endless.