 Completing any four stages unlocks the next five, and they do not have to be completed in any order or in sequence.Thus stages 1-10 are available to play after completing any four stages from 1-5 and stages 1-15 are available when any eight stages are completed until finally all 100 stages are available to play after any 76 stages have been completed.This means that player can choose to skip one stage out of each set of five and still be able to play stage 100.