Portal: Reloaded

Not to be confused with Thinking with Time Machine, which involves the use of a time machine.

Portal: Reloaded is a Portal 2 mod that features three portals instead of two, the third being a time portal that jumps time 20 years into the future. The mod features 25 new puzzles into the game, all of which requires the third portal. The mod is free on Steam, but it requires the user to have Portal 2 in the library bought and installed.