In brief: Portal fans, rejoice! A small team of developers who call themselves Second Face Software have published a new mod for Portal 2 that adds more than eight hours of original content to the base game.

Portal: Revolution is a free-to-play mod that chronologically takes place before the events in Portal 2, in an environment the team describes as the dead and decaying Aperture facility.

The mod's description says it includes over 40 original puzzles that make use of new elements, and leverages existing mechanics in a way not seen in Portal 2. Highlights include a new laser cube variant, a gel cleansing field, the return of the "pneumatic diversity vent" element, and 15+ puzzles that use only the blue Portal-Gun.

As for difficulty, the team said the mod "starts where Portal 2 stops" but assures players they will be educated about new mechanics and tricks before being thrown into the fire. Everything has been rigorously play tested to ensure the puzzles are not too tough; none require advanced tricky movement, and only a few call for portals to be fired mid-air.

Depending on your proficiency with Portal 2 mechanics, the mod could be good for anywhere between five to eight hours of playtime.

Portal: Revolution was originally expected to drop on January 5, but the team hit a minor speed bump along the way. The game was submitted to Valve on December 20 for review (all games on Steam have to undergo review before they can be released). The devs were told that a small team of reviewers would be available during the holidays, and to expect some delays.

Fortunately, the holidays only held things up by one day, and the mod has since been given the green light.

Portal 2 is the 2011 successor to Valve's first series entry from 2007, itself a spiritual successor to a game called Narbacular Drop that was a senior project from a group of students at the DigiPen Institute of Technology.

If you don't already have it, Portal 2 is currently available for $9.99 over on Steam.