Portal: Timestall is a free Portal 2 mod that follows the story of a test subject that is a part of Apertures lost time travel experiments. After something goes wrong you are lost in time and must advance through a new era of Aperture Science to stop time from collapsing. Timestall features a campaign that rivals Portal 2s in length, providing a fully voice acted story and brand new time based mechanics. Solve all new puzzles with the help of time slowing and time pausing while trying to figure out how to get back home and stop time from collapsing in on itself.
Cave Johnson here, Once I was walking down the street and I saw a fancy photo of shower curtains. I bought several shower curtains that day. This is our fancy photo. Give us money.