A controller for an electronic system includes a tracking member fixed to a controller body. The controller body has a head that adjoins a handle at a neck region, and that includes at least one thumb-operated control. The controller includes a hand retainer that in a closed position is configured to physically bias the user's palm against an outer surface of the handle. The hand retainer includes a resilient member that biases the hand retainer towards an open position. The resilient member is attached to an anchor that is attached to the head by an adjustment mechanism that permits the resilient member to be moved towards or away from the user's purlicue. The tracking member includes transducers that are coupled to the electronic system by electromagnetic radiation. Proximity sensors, spatially distributed on the handle, are responsive to a proximity of the user's fingers to the outer surface of the handle.