ON-SETS is an exciting and colorful resource allocation game that teaches set theory - the foundation of modern mathematics. Using game rules similar to EQUATIONS, players in ON-SETS explore the concepts of union, intersection, difference of sets, complement of a set, set identity, set inclusion and the null and universal sets. ON-SETS captures the same creative problem-solving and strategic intrigue as EQUATIONS and WFF 'N PROOF. The basic game can be taught to six-year olds. As players develop skill, it becomes more sophisticated and ultimately expands to levels that will challenge intelligent adults. The complete set involves thirty different game levels. The whole family will enjoy exploring this fascinating approach to learning the fundamental ideas behind all mathematics.