The child’s learning surfaces are a perfect place to control complexity. Put yourself in the child’s shoes as you assess the complexity of the environment. Is there glare, distracting movement, multiple colors in the a background or is there a good solid color background to get a good look at the important learning materials?
Here is a picture of a clear tray that comes with most wheelchairs. It is a terrible surface for optimal visual abilities. The child sees moving legs (movement and multiple colors), the tray produces glare and provides no solid background.
Here is a solid black background that takes care of the problem. It is made of black plastic and attached with velco.