There was a little bit of confusion as to what 'Portal: Still Alive' was when it was announced during the Microsoft press conference. Now they have finally revealed just what it is.

According to the new Xbox.com splash page - the game is the original Portal single player game, complete with GlaDos fight and all, and the song of course.

Along with the regular experience, the game will also contain a new 'challenge mode' for the veteran Portal players who are looking for that extra challenge. The original PC title also included some challenge levels, but only included six. It appears that they'll be expanding on this quite a bit.

The best information for me is that this means that the download limit will be expanding once again. Portal would have to be something roughly around a gigabyte realistically due to the Source engine. It will be interesting to see just how this game will be dealt with, and not to mention the price, which I would assume might be around the 1600 Point mark.

[Psst, Valve! Do Half Life 1 next!]

Source: Portal Xbox.com Splash Page