Copyright (c) 1980s ?? 

The game is played on a 7x7 board, with the following setup:

MOVES - A move consists of either a "growth" or a "jump". 
A growth is a drop of a stone on an empty adjacent (orthogonal or diagonal) empty cell. 
A jump is when one stone already on board moves to an empty cell that is two positions away. This includes diagonals and "knights moves".
Once placed, any opponents adjacent stones to the new piece (either through growth or jump) are flipped to the moving player's color.
PASS - A player who cannot move must pass.
GOAL - Wins the player with most stones at the end of the game.
An example

If White jumps to [1], the 2 adjacent black stones are flipped. If a black stone jumps to [2], both white stones are flipped to black.

This game can be easily extended to 3 or 4 players, and also to larger boards. With hexagonal boards, a growth is a move to an adjacent cell, and a jump is a 2 cell move (check Hexxagon which also has a ZRF). Check here for more information about Ataxx.