Cancelled Portal prequel F-Stop rebuilt into nearly complete playable game

Leakers have assembled a nearly complete, playable version of F-Stop, a cancelled Portal prequel, after missing files reportedly appeared in a Valve fan Discord. The recovery gives players a chance to see a project whose ideas only partly surfaced in Portal 2 and whose mechanics differ sharply from the main series.

F-Stop centres on a camera that captures objects in photographs, which can then be used to place those objects elsewhere. Most of its assets came from a 12-terabyte leak in August, while source code and map data were reportedly shared later; videos of the full campaign run for less than an hour. Valve developed it during a three-month experimental period in 2007.