+ li.
+ "Capturing" a friendly unit pass the ball to it, or take the ball
+ from it. In both cases the pieces don't move.
+
+p.
+ All pieces represent players on a field of some ball game,
+ so they can move up to three squares only for a better realism.
+
+p.
+ To balance the advantage of ball possession, the piece holding the ball
+ cannot capture enemy pieces.