My cat (Fluffy) has his own territory of raised platform with good window viewing, plus many other areas where my 2 year old son (Hugo) has generally restricted access or not permitted.
Fluffy is a 5 year old Norwegian Forest Cat. We currently have a 2 metre long box in the kitchen and Fluffy camps in at times. The play is Fluffy runs in one end and Hugo chases him. Fluffy runs out and then back in. In other places, whether Hugo chases Fluffy if he wants to get away, then we let him through a door (Hugo can't pass) to upstairs. So far with the box-play Fluffy doesn't do that, but what other signs might I look for that he stressed by the "play"?
Fluffy is pretty nice - he plays for a few minutes a day biting a doll.