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; and 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.