This animated background is synthetically generated and rendered under HTML text as a windowless control. The media used is 6.3KBs in size. The JScript is under 100 lines long.
Four spot lights are animated using 2D paths and are pointed at an open room that is viewed with a perspective camera and a static, purple, pointlight source. The spot lights tilt gently towards the wall as they approach them. Lastly, the result of the 3D rendering is tiled to produce the final background.
Pressing the left mouse button first halts and then restarts the animation.