Multi-layer display system and its control method

A display control system for a multi-layer display system including at least one multi-layer display unit (6). A multi-layer display unit includes multiple stacked or overlapping display layers (1a, 1b, 1c, 14, 15) each adapted to render display elements (2, 16B, 17B, 18B) thereon for viewing through the uppermost display layer. The level of difficulty for a user to view an overlapped image differs depending upon the colour, brightness or type of image (for example text-on-text) being displayed and also the layer on which the image is being displayed and also whether the image is currently active. At least any overlapping portion of display elements from different display layers are adjusted (automatically or by the user) in order to improve the viewing experience for a viewer. Types of adjustment possible include moving the images within their display layer or to an alternative display layer or alerting their visual properties (such as colour, brightness, contrast, etc).