Can you prevent the background from clearing

I'm trying to do somthing strange, prevent the game from clearing the screen so that everything on it would leave a trail (somthing like when win95 would crash and you would drag windows around =D)

I'm thinking that combining this with particle effects and additive blending would cause an explosion of colour which would gradually turn the entire screen white.

I've been fiddling around with the "Clear Background = no" setting but I'm not getting it to work. Can this be done and how.

I figured it out. Apparently, apart from the obvious like having "Clear Background = no" having no background and setting all layers to "transparent = yes" the WebGL has to be off.

This is the result. (Can't post links yet)

imgur.com/AXXQam1

Looks freaky =)

If you create a layer underneath every other layer and add a black sprite (not background) that covers the whole screen but has only 5 alpha this is the result:

imgur.com/hpnh0mc