This is a free first-person puzzle mod for Portal 2 built around a single new mechanic: a handheld time machine that records your movements and then plays them back as a duplicate of yourself, letting you cooperate with your own past actions to solve test chambers. You still carry the portal gun and work through Aperture-style laboratory rooms using buttons, cubes, lasers, and portals. There is no combat and nothing is harmed; the challenge is entirely spatial and logical. The mod is short, has essentially no dialogue or story, and includes no custom voice acting.
The game frames its content as a pure logic puzzle. Success comes from planning and coordinating two synchronized versions of the same character, with no conflict, stakes, or subject matter beyond solving the test chambers.