Steam's midweek madness deal is thoroughly delicious. I'm being so sincere right now. Just over a fiver for Portal 2 has got to be worth paying if you haven't yet checked out this sensational puzzler, widely heralded as one of 2011's best games.
Note that you can also get the original Portal for £2.37, a double pack for £6.11, or two copies of Portal 2 for £8.49. Cheap as chips. Thanks to gambe1984 at HotUKDeals.