RPGs as games

Reading Geoffrey Englestein's collection of gaming essays today and came across this rather innocuous definition of what a game's rules are and do:

"A set of game rules is a logical construction. The rules tell you what you are permitted to do, what you are prohibited from doing, and how the state of the game - scores, locations of pieces, etc. - all change as a result of the players taking an action" (pg. 59 of GameTek)

This drove home for me how RPGs are really no different from other games. In RPGs, the fiction is the playspace (the equivalent of the board or cards or whatever - the canvas on which the game is played). The rules tell you how you can legally affect the fiction, and the fiction changes as a result of those actions being made.