The challenge is to bring sixteen animals (four each of lions, hippos, giraffes and camels) safely across the river (the left-side edge of the playing board). There are 60 opportunities, ranging through five levels of difficulty, to do so. Each puzzle has a different layout on which to place the animals in their starting positions. After the first animal crosses, each succeeding one must be either the same color or the same animal as the one it follows. Although this is intended as a solo puzzle, players do enjoy cooperating in finding the solution, particularly since it's hard to tell whether you're on the right track until only the last few animals are left.