I had a concept for mirror blocks, more the most part, they are purely asthetic. They wouldnt really show a reflection of the player, because that would look weird. but the block would make to clear that it looks like the mirror. The special properties come into play when a portal gun is fired at it. If you fire a portal gun at it, it will bounce off the mirror blocks. Sloped blocks would change the direction of the portal projectile obviously. Thought this could be cool and add another aspect to portal guns.