constriction sphere table lamp

This is the mechanical design part of my lastest project: building a lamp without any visible or touchable controls. It is turned on and off (and dimmed) by simply rotating the lamp itself around its vertical axis.
But any other idea can be realised as well by applying some sort of lamp insert on the base part. It has two holes (50mm distance) for mounting screws - feel free to make your own lamp insert working :-)