Portal 2 is the followup to Portal which was originally a pack in the the Orange Box. Portal 1 could not have held up as a stand alone product which is why many people were doubting Valve’s decision to make Portal 2 a full retail game. The original Portal only clocked in around three-four hours, which as a pack in with four other games is long enough. Portal 2 is full price and it is a full length game. First play-through of the single-player netted me around eight hours. The single-player could have been all this game had to offer and it would be worth the money.