This is Tessallation, a free puzzle game where you play with yourself. Well — copies of yourself.
You play as Tessa, a schoolgirl with a cube for a head (don't ask) who has the ability to time travel. But it's not just any ordinary time travel; Tessa can travel back in time while leaving a copy of herself behind.
She might, for instance, come upon a door operated by a button. She can stand in front of the button for five seconds, push it, then travel back in time, move in front of the door, and quickly step through when her copy pushes the button. Hence "Single-Player Co-op" — where timing is just as important as figuring out the puzzles themselves.
Tessallation is freely available here, and should be a great distraction if you crave some mind-bending puzzles.
Tessallation - Game [Wordpress]