Cutting holes with projectors

Hello,

was going to put this in the forum... but after several attempts it didn't seem to add the thread...

Anyway

I'm working on a project which I'm hoping to export to Android and IOS (though currently don't have resources to export to IOS), i'm using unity free.

I'm trying to get a spotlight effect on-click; so you can click around the screen and light up areas under the mouse momentarily. I've used spotlights to get this effect, but it's not very pretty or efficient and you get dodgy shadow and shading problems (which amplify on mobile)

I'm now trying an alternative method; the scene is lit, with a black overlay on a different depth in which you cut holes to get the same effect. it works really well (perfect it is not, but I'm pretty happy with it). I'm using the shaders from [URL="http://forum.unity3d.com/threads/35808-Projecting-a-hole?p=289374&viewfull=1#post289374"]This Post[/URL]. I've simply changed the colour of the "receiver" shader to black (pretty much the extent of my shader knowledge right here) and added a radial alpha gradient.

My problem is that after tests it doesn't seem to work on android (and I'm guessing the same will be true on IOS too). I would like to learn shaders eventually but my current knowledge doesn't allow me to know why it doesn't work or how to go about fixing it (or even if it can be at all). If I can't get this method to work I'm all out of ideas on how to get this effect at all. :(

Thankyou, I really hope you can help :-?