Expanding on Huizinga’s work, and examining the subject of play
from other angles, other theorists such as Roger Caillois (1958), Jean
Calvet (1978) and Georges Hourdin (1961) worked on categorizing play
into its various forms, distinguishing between free play and structured
play, as well as between how children and adults play. This paper will
Vol. 21 No. 1 : David: The Shift from Outdoor to Indoor Play 75
deal with free play among children and youth only.