ON-SETS is an exciting and colorful resource allocation game that teaches set theory–the foundation of modern mathematics. 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 players as young as six; as players develop skill, the game becomes more sophisticated and ultimately expands to levels that will challenge intelligent adults.