Portal Stories: Mel is now available on Steam, offering a free modification for all owners of Portal 2 to add new gameplay to the first-person puzzle sequel. The announcement simply says: "After years of hard work Portal Stories: Mel is now finally released! Featuring 22 levels full of brand new tests, dialogue and much much more!" You can have a look in this launch trailer, and here's a description:

1952, in the early years of Aperture: Science Innovators, Cave Johnson’s scientists experimented with whatever they wanted. Not everything worked as it should have though, but that wasn't going to get in the way of the progress of Science! Mel unfortunately took part in a faulty test called the Aperture: Science Innovators Short-Term Relaxation Vault, falling asleep for years. When she finally wakes, there is a fake Cave Johnson telling her she needs to escape the facility and a new device called the Aperture Handheld Portal Device, her mind races with questions. “Who is this imposter Cave Johnson?” “What happened to the facility and its staff?”

"What happened to me?"

Main Features

• 22 levels, with an estimated gameplay time of ~6-10 hours
• Custom Story with 350 separate in-game voicelines
• Over an hour of custom music with the Free soundtrack included
• Huge amount of custom assets
• 27 steam achievements
• Standalone mod (You do not need Portal 2 installed to play)
• Free to Play (You must own Portal 2)
• Logic based puzzles, not execution based puzzles