This game board is an array of tiles. The tiles have letters. The game play involves flipping a pair of letters, as if the two tiles can move through the screen on the axis that connects them. In any case, they move switches them. The goal is to rearrange the tiles to spell words.
cat --flip c:a--> act
dog ------------> dog
cat --flip c:d--> dat
dog ------------> cog
The game can be played different sized boards, and with boards with cutouts.
Variation 1: Have the tiles have both color and a letter, to distinguish common letters.
Variation 2: Have the tiles be two sided, so that flipping them exposes the other sides.
What is interesting about this is that it is a class of games easy to implement in the computer but which is hard or impossible to implement as a physical game. There is a whole class of variations on pen and pencil or board games that haven’t been tried because of this!