How is this created? 3d background with movement

[nellipope]

Came across this, in a rather roundabout way, was wondering how the background was created to move with the mouse.
Admittedly this is way beyond my meagre web building skills, but thought it was great effect.

CBeebies Land

 

[hankscorpio]

Right click and go to the view page source it was done by javascript.