Portal

Portal™ is a new single player game from Valve. Set in the mysterious Aperture Science Laboratories, Portal has been called one of the most innovative new games on the horizon and will offer gamers hours of unique gameplay.

Region: Global. Check that the key's region matches your Steam account's country before buying — region-locked keys can't be activated elsewhere.

What you get: one unique, unused product key, shown on your order page (and in your account) once payment is confirmed — usually within minutes, and at most 24 hours. No physical item is shipped.

How to activate: open the Steam client, choose Games → Activate a Product on Steam, accept the subscriber agreement and paste your key. The game then appears in your library, ready to download.

Requirements: a Steam account and the Steam client. System requirements are set by the publisher and listed on the game's Steam store page.