Tue, Apr 12, 2011 | 22:21 BST
Portal levels added to The Ball, Killing Floor and Audiosurf through Valve’s Potato Sack-ARG
Valve’s Portal 2 ARG, a.k.a. the Potato Sack, has been updated to include The Ball and other games with added Portal themes.
Audiosurf was also updated with Portal themed levels and artwork, The Ball was given a new level called Aperture, and Killing Floor has a Portal-themed prototype level as well.
All of the Potato sack games are still on sale. Go get some.