Digital distribution platform Impulse, which was purchased by GameStop last year, has started selling Valve games like Portal 2 and Left 4 Dead via its online store. This is a first for Valve digital downloads, which previously were sold only on Valve's own Steam platform. The games currently cost the same on both services, although we imagine sales will be conducted separately. On the one hand, it speaks well of GameStop and Impulse that Valve considers the service important enough to break its long-standing Steam-only policy to sell games on it. On the other, the games are still going to require the Steam client to play, so we're not sure how much it benefits anyone to throw an extra company in the mix — especially if people will have to download Impulse's software as well.