game(s) -- ludic marker(s)
... / design(s) / emergence(s) / exercise(s) / _ / .
... if the game can be identified easily as play, then it should be easy enough for bystanders to accept or refuse an invitation to play.
The adoption of ludic markers is the easiest way to sidestep some ethical questions. ... ludic markers need not be explcit but can focus on communicating playful or fictional aspects of the game.