Modern dance was created in the early 20th Century as a reaction to Ballet's strict rules and confining shoes. Dancers wear loose fitting clothing, bare feet and tend to focus on moving into the floor. Dancers use strength and flexibility to execute dynamic movements. Flexed feet and bent knees have been the symbol of Modern dance, but post-modern movement has moved into the mainstream, and many dances using the title "Contemporary" from the hit show SO You Think you Can Dance use the roots of modern dance.