Portal free on Steam until September 20th

Now you're thinking with discounts!

Original Portal available to all Steam users free until Tuesday, September 20th

As if the next few months weren't going to be distracting enough for gamers, Valve have gone and made its first-person puzzler Portal available to all gratis on Steam until Tuesday the 20th of September.

Portal, which launched back in 2007 alongside Team Fortress 2 and Half Life 2: Episode 2, went on to be a surprise runaway success, scoring 95 out of 100 on Metacritic across Xbox 360, PlayStation 3 and PC and leading to the equally well-received Portal 2, which picked up the Best PC Game, Best Xbox 360 game and Best PlayStation 3 game at the 2010 E3 awards ceremony.

Trapped underground in the abandoned laboratories of the sinister Aperture Science, players must navigate a selection of testing chambers using a pair of reality-bending connecting portals. Standing between the player and freedom are roomfulls of poisonous goop, chatty machine gun turrets and a sociopathic robot invigilator with a fondness for neurotoxin.

Would-be test subjects eager to further the cause of science need only download a copy of Steam and search for Portal to get in on the action. Missed out on Portal the first time around? Check out the teaser below for a look at what all the fuss is about.

Portal teaser trailer