Steam now offers the opportunity to pre-purchase BioShock for digital download, which includes a pre-load of Irrational's eagerly anticipated first-person shooter so it can be played as soon as it officially debuts on August 21. Update: Valve responded to our question about what time the release would occur, saying it would be at 4:00 p.m. Eastern time, and that there is now a ticker on the front page of the Steam Website counting down to the release.