Abstract: Systems and methods are provided for conducting games or other interactions between networked computers, mobile devices, or other such client devices. Players compete via graphical elements, termed “devices”, that move and engage each other on top of existing windows, such as on a player's PC desktop or mobile device background. The devices may be tanks, spaceships, characters, or any other graphical element that can take part in a game or interaction. The system and method provides for short-term, casual, online games using light clients or instant messaging protocols. The games may be played quickly and easily, with minimal interruption of other endeavors. Players may conveniently choose opponents via a friends list, lobby system, or other such method, in an easy-to-use, e.g., drag-and-drop interface.