Game play is a procedure of playing the game following the results of choices existing in the game. Such games are generally implemented not by certain rules and techniques like other designs but by abilities and experiences of game designers. In this paper we propose a design method of game play through possibility reasoning and distributions using elements of cognitive psychology which are 'a theory about problem solving' and 'a theory about reasoning and decision'. These two theories are very closely related to game play which has the procedure of solving problem of continuous choices and their results.