Similar to Muggins!! but more advanced math.From the manufacturer:In Opps players add, subtract, multiply, and/or divide the integers rolled on the dice to produce an available answer to create runs of 2 to 5 marbles in a row of to block an opponents attempt to build runs. Bonus points are scored for runs of 2 to 5 of the player's marbles. Highest total score wins the game. Countless possibilities surface with positive and negative numbers. The regular game directions are given first, followed by easier and more complex variations. - BoardGameGeek