locomotor, friendly intent/play signals, 3 developmental phases of physical play: rhythmical stereotypes (boys engage more than girls, in babies, improve control of motor patterns, kickign/waving), exercise play (about learning, jumping/climbing, releasing energy, improve strength and endurance), rough and tumble (play fighting, learnt around school age, releasing energy, loosing and loosing, teaches social structure, understanding emtoions as paretns pretend to be hurt, teaches boundaires)