1. A method of controlling a computer game system comprising: displaying a computer game at a display viewable by a user of the game, the display comprising at least one avatar and an environment; receiving manual input from a hand-operated controller operated by the user; receiving a stream of images from an image capture device depicting the user; displaying a portal as part of the displayed computer game, the portal being a region of the display representing the stream of images depicting the user; recognizing a gesture of the user by analyzing the stream of images; controlling the display of the avatar on the basis of the manual input and controlling displayed interaction between the portal and the environment on the basis of the recognized gesture of the user; and one or more of: recognizing a gesture of the by analyzing the stream, of images further comprising the recognition being based at least in part on tracking the location of at least one body part of the user in the stream of imaged, determining whether the at least one body part being tracked is located within a predefined portion of the stream of images wherein the predefined portion is a predefined distance from an edge of the stream of images; recognizing a gesture of the user further comprising determining whether the user is holding the controller with both hands by comparing the stream of images depicting the user with at least on pre-recorder stance example; recognizing a gesture of the user further comprising determining whether the user id holding the controller with both hands by tracking a location for the hands and determining whether they are within a predetermined distance of each other; or recognizing a gesture of the user by analyzing the stream of images, determining that the user is reaching out to an edge of the portal, and rendering a representation of a body part of the user outside the edge of the portal.