It may be short, but Portal's unique puzzles will keep bringing you back for more.
For those of you who are unfamiliar with this game, Portal has you take control of a girl in a test lab who is being guided by the real star of the game, GLaDOS, an AI who controls the facility. You eventually get a gun that shoots portals that will help you throughout the game. You can get from one area to the next by simply shooting both portals and walking right through. There other tricks you need to learn like falling through the portals and build momentum to get over a gap. In other words, "speedy thing goes in, speedy thing comes out". You will also need to figure out how buttons work, avoid turrets who will shoot you on contact, and you must guide energy balls to open certain doors. The gameplay overall is very unique and the puzzles are fun and sometimes challenging.
The game's story is very well written too and quite funny, mainly GLaDOS' dialogue throughout the game, especially the final fight. During the credits, she will also sing "Still Alive" as one more taunt toward you. The song itself is quite witty and clever.
As for this version, Portal Still Alive offers new puzzles for you to play through. Not only are there brand new puzzles but there's also more challenging versions of the original puzzles from the campaign. For instance, one puzzle makes you do the level without touching the floor and at least two other levels put turrets in cages so you can't kill them. These levels are very challenging, even the newer ones, but there as fun and unique as ever. I am disappointed that there is no new dialogue from GLaDOS though, that would have made playing through them better.
The only major problem with this game is the length. The game's campaign can be finished in a little over an hour. Other than that, Portal is one of the best games this gen with it's original gameplay and puzzles. The newer levels are a great bonus if you want the XBLA version but if you already own the original Portal, either in The Orange Box or just as a stand alone game, then there isn't too much you're missing out on here. If you haven't played Portal before, than I highly recommend this version.