This is very cool. I enjoyed Sin Episodes #1 and was thoroughly disappointed with Half Life Episodes #1, but this is a real breath of fresh air. Also good to see someone has finally made something which makes the Doom 3 engine look good. The portals are really cool, much better than I imagined they would be, and I love the enemies appearing out of them. Good use of the "puzzles" ( simple, yes, but a little variety ) and the whole gravity thing is really cool too. Quite a big demo too. Very impressed. I'll be getting this.