Deep Play and Flow
Two different and still similar sounding references to play. Diane Ackerman on Deep Play:

Ancient people had their own forms of deep play, Ackerman said, and termed deep play to be rapture and ecstasy. "Rapture is being seized by force ... rape, ravage, usurp," she explained. "Ecstasy is a Greek word meaning a symbol of standing, or to stand, outside oneself. When you are experiencing ecstasy, you fly out of your mind and watch the known world dwindle in the distance."

and Mihaly Csikszentmihalyi on flow:

Mr. Csikszentmihalyi describes flow as "being completely involved in an activity for its own sake. The ego falls away. Time flies. Every action, movement, and thought follows inevitably from the previous one, like playing jazz. Your whole being is involved, and you're using your skills to the utmost."