A computer implemented method of controlling a user interface of a computer device which is responsive to user engagement with displayed player objects on the interface. The method comprises steps implemented by computer executable code (executed by one or more hardware processors on the computer device) and encompassing, but not limited to, displaying a game area with a number of game objects in a static player graph as well as providing a player object which can be selected to target and shoot game objects in response to player behavior or to contribute directly to a game objective. A boost action is triggered when game objective is fulfilled.