Alongside the announcement of Steam pre-sales for XCOM: Enemy Unknown, 2K has released a gameplay walkthrough narrated by lead designer Jake Solomon. Things don't start out looking very good for humanity ... until Sid Meier's psionic powers turn the table, that is.

In addition to the new video, we also have the first screens of Enemy Unknown's PC version. Apart from the obvious point-and-click differences, the PC version also features a traditional grid system, which should be familiar to fans of the series.

Finally, 2K has announced that digital pre-orders for Enemy Unknown are now open. In addition to Steam's pre-order promotion that Valve revealed yesterday, the downloadable version of the game is available from other outlets as well, including GameStop and Amazon. As with its retail counterpart, pre-orders of the digital version include the "Elite Soldier Pack," which features the original X-COM flat-top hairstyle, among other soldier customization options.