While the concept of working with past versions of yourself is nothing new, the execution here is stellar!
The pixel art looks good and maintains a consistent style throughout. The sound design is potentially a touch lacking, but what is there sounds good and communicates information effectively. Plus, it sounds great when the actions of a bunch different you's start piling up. Saving the best for last, is the puzzle design. The puzzles in this game really got me thinking, and they all had satisfyingly solutions once you explored enough to get your head around them. Excellent job with this game!
The only issue I encountered was that sometimes the cubes would get caught on corners if I wasn't careful, but otherwise it played flawlessly.