1. A method of interfacing with a machine, comprising: generating position data describing a respective current position of each of one or more game objects in relation to a playing surface defining a boundary of a field of play of a game involving use of the one or more game objects in the field of play; displaying on the playing surface a graphical interface image; determining whether the position data in relation to the displayed graphical interface image satisfies an input instruction predicate; and in response to a determination that the position data satisfies the input instruction predicate, executing the input instruction on the machine.