In this interactive from WNET, shut down a series of creature-controlling machines by determining the solution to a function. When changing one quantity determines the value of another, they are connected by a rule you may not see. Find the rule and you can predict any outcome. In the accompanying classroom activity, students use a deck of playing cards to see if they can use what they learned in the interactive about rules, functions, and numbers in another game called "Mystery Envelope." This resource is part of the Math at the Core: Middle School Collection.