Here is another variant played by many farm kids and inspired by an tale:
2 farmers only have 1 field and 1 groffel each.
One is covered with coal (black) the other one with floor (white) and each time they move, all the groffels around are covered the same (converted into the moved piece color). Groffels can lay eggs that are of their color and that hatch and change the color of groffels around. Or they can make short jumps changing the color of groffels around the place they land.
Starting positions
X..
.....
.......
.......
.......
.....
..O
Each turn the groffel can lay an egg next to him or make a short jump.
.....
.ooo.
.oOo.
.ooo.
.....
in this diagram O represent the groffel, o a possible place for an egg and . a place to jump to.
-If the groffel jumps the O position is freed (the piece moved)
-If it lays an egg, a new piece is added
Converting oponent pieces:
All the oponent groffels (pieces) around an egg (adjacent in 8 directions) are changed to your color.
Or, for a jump, it's the oponent groffels (pieces) around the landing square.
Pass: If there is no free place to jump to or lay an egg you must pass your turn. Groffels can't jump farther that 2 quares in each direction.
The winner is the one with most pieces of his color when there is no more empty quare.
If all the pieces of a player are converted at once, he lose and is forced to offer free drinks at everyone

Tactics:
For defense, add eggs to cover the field, the ones surrounded by your own color can't be converted in 1 turn. 2 lines of your color are impossible to jump over. So use the field border to
Attack ; Don't let the other create such strong positions and jump out of them before being surrounded. You will leave an empty space he might need to fill, leaving you the advantage of attack on your next turn. Don't attack too soon or you can lose all your groffels at once.
I only tested once, it give good reversals of positions and scores. Each party is not too long.