I've never really gotten into playing custom levels for Portal 2—I just don't find the game that much fun without the inclusion of Wheatley, Cave Johnson, and GLaDOS. That's why it's great when Portal 2 mods add something new to make up for what's missing. In this case, the added element is a hand-held time device that lets Chell make a time-shifted duplicate of herself, and team up with it to solve puzzles. Thinking with portals is no longer enough, now you're Thinking With Time Machine.
Thinking With Time Machine
Steam's Portal 2 Workshop is filled with unique twists on the space-bending puzzler's central mechanic. With such creativity lurking in the primordial soup of the Workshop, it would take something special to crawl out and into the main Steam storefront.
That something is Thinking With Time Machine, and it fits the bill for two reasons. Firstly, it introduces a new time recording mechanic, in which you can replay your actions to create a temporary clone in-level. Secondly, it lets you look at your legs.