In Antwort auf:

Umm so the shader uses the alpha of my skin to "mirror" the envrionment?



Yes, he does. With the alpha channel you control how much shader and how much skin you want to see (white => 100% shader, black => 100% skin)

You can even try to make it look like a real mirror: Using this script you can make a +6 cubemap directly from your level. The only disadvantage is that it doesn't work with animations or anything that moves (this is a pro feature).