Rummy has given rise to a wide variety of variants, each with distinct rules and strategies for play. Gin Rummy, which was created in the early 20th centsata kimgury, is among the most well-liked variations. In Gin Rummy, players try to make runs & sets, but they can also "knock" if they think their opponent has more unmelded cards than they do. Players must choose when to end the round depending on the strength of their hand, which adds another level of strategy.