When we took an overview of the remarkable happenings in the potato sack ARG yesterday, the trail was going cold, and it looked as though things were winding down. For a few hours at least, they were, then it all kicked off again. New updates have added Portal 2 themed levels to many of the games in the potato sack sale. The voice of Glados has started appearing in menu screens and secret messages, and to top it all, Bit.Trip Beat creators, Gaijin, dropped a heavy hint that completing the ARG could cause Portal 2 to be released early.

Adding fuel to that theory, today Portal 2 became available to pre-load through Steam. We've collected videos and screenshots of the new Portal 2 themed levels from potato sack sale below.

The Ball



The Ball gets a good extra hour of free Portal 2 levels, including one devoted to bowling over Aperture Science turrets. The team have done a great job of recreating Portal 2's assets in the Unreal 3 engine.
 

Audiosurf



The Portal 2 update in Audiosurf replaces your ship with a portal gun, and adds companion cube blocks to the courses. The best update is the addition of new Portal 2 songs like the one in the video above. After a couple of listens, it really gets stuck in the brain.
 

Bit.Trip Beat



Glados has well and truly invaded Bit.Trip Beat with this difficult new level. Gaijin hinted in their latest blog post that more ARG clues will be revealed to those who achieve perfect completions of the new levels.
 
 
AaAaAA!!! - A Reckless Disregard for Gravity



Glados has a lot to say about falling off tall objects after the latest Portal 2 update to A Reckless Disregard for Gravity. Creators Dejobaan also created a brilliant overview of the progress of the ARG so far, ending with Glados' invasion of the potato sack games.
 

RUSH



What better way to combine Portal 2 with Rush than to add companion cubes? It's almost as cute as the Portal 2 level in Toki Tori below.

Toki Tori



Toki Tori's levels provided plenty of useful clues during the ARG. Their silhouettes formed decipherable codes that helped to unlock the passwords for the Aperture Science login screens. The new level has Glados hanging in the background, watching your every move.
 

Killing Floor

The new Killing Floor map has you fending off waves of zombies in a massive new Aperture Science map. The familiar human vendors have been replaced by a robot that looks just like one of Glados' personality spheres. It looks great, too, with its overgrown test chambers and giant buttons. You'll find their official screens of the new map below.

The potato sack sale is still going, offering 13 great indie titles at 75% off. You can buy each one individually for 50% off while the offer lasts. Head over to Steam to take advantage of the deal

The Potato Sack sale kicked off over the weekend on Steam. The sale knocks 50% off 13 indie games, including Super Meat Boy, Amnesia: The Dark Descent, Killing Floor and more. The whole bundle is 75% off, and you'll get a potato hat in Team Fortress 2.

This isn't just an ordinary sale, thought. There's something weird and potato related happening. Several games in the potato pack have received some unusual updates. Egyptian hieroglyphics have been found in Amnesia, potato references have been found in Defence Grid: The Awakening, and plugging a Razer peripheral in to Kick It! will trigger one of fifteen potato related phrases like this one "never trust a potato...they have eyes everywhere. They are always listening...we never went to space! SPUDnik was a Russet Conspiracy!" What the spud is going on?

VG247 note that a wiki has been set up to collect the mounting clues, though nobody has any idea where any of it is leading. Valve revealed Portal 2 through a series of encoded images and radio messages patched into Portal 1. Could there be another reveal on the cards, or is it all an elaborate, long running April fools hoax?

Here's a list of the games that are part of the potato sack sale. Head over to Steam to take advantage of the deals. There's no end date for the sale yet.

1... 2... 3... KICK IT!
AaAaAA!!! - A Reckless Disregard for Gravity
Amnesia: The Dark Descent
AudioSurf
BIT.TRIP BEAT
Cogs
Defense Grid: The Awakening
Killing Floor
RUSH
Super Meat Boy
The Ball
The Wonderful End of the World
Toki Tori