Abstract: A user interface including a display driver and a control unit having a rotatable actuator. The display driver is configured to cause a display to display a plurality of selectable categories in a main array extending in a first direction, to display, for at least one of the categories, a respective plurality of selectable subcategories in a respective subarray extending in a second direction different to the first direction, to selectively highlight one of the categories and subcategories and to move highlighting between adjacent categories or subcategories in response to rotation of the rotatable actuator. The control unit includes an orientation sensor configured to detect whether the control unit is in a first orientation or a second orientation.