This invention pertains to a multipass retroreflector and to a method for its operation. The valve assembly includes an actuator housing enclosing an actuator piston and defining a counter-biasing chamber and a first control chamber on the same side of the actuator piston, and a first pressure control port in fluid communication with the first control chamber. The memory comprises code executable by the processor to display a scrollable list of items on the touch-sensitive display, to detect a first touch gesture over the scrollable list of items on the touch-sensitive display, and, in response, to scroll the scrollable list of items on the touch-sensitive display.