A very fun Portal experience. The puzzles are good and I like the new elements they introduce. The level design is very good - there is very little chance of the player becoming hopelessly lost and having no idea where to go, which a lot of fan-made projects have the habit of falling into. This game feels very good and very professional. Its story is fine - nothing particularly earth-shattering by any means, but perfectly acceptable. I would say this is absolutely worth a play if you are into Portal, or just Valve games in general.