Portal: Revolution, a hotly anticipated fan-made mod for Portal 2, was set to release on January 5th, but its developers recently put out a statement announcing that the mod would be delayed.
The delay announcement explained that while the game's development was completed, it was submitted for review to Valve over the December holidays and the review process was not completed (or even begun) by the game’s release date of January 5. Fortunately, Valve began that review process shortly after the news was published and the game was officially released just a day later.
Developed by Second Face Software, Portal: Revolution is a fan-made prequel campaign said to offer over eight hours of gameplay across 40 new test chambers and includes voiced characters as well as new puzzle mechanics. The developers suggest the new puzzles will be more challenging than what fans played in Portal 2, but players should be eased into the new mechanics over the course of the game.
Portal: Revolution is now available on Steam, though players looking to play it will first need to own Portal 2. The good news is that you can pick up Portal 2 for $0.99 right now and through January 11.