Interesting concept. I think the idea of using your past lives to help you move forward, and I can see a lot of interesting puzzles being created with it. Also you did a good job with creating levels and tutorials that ease the player into the game and teach them the main mechanics.
Somethings that could improve the game is someway to completely restart the level without just making a copy of yourself. I often got into a situation where I immediately knew I made a mistake, but seemly had no way to completely reverse it. I ended up with a huge field of old runs that I couldn't get rid of. It is a small thing, but I think it could have a big impact on gameplay.
Also I love the art style, but I think the character felt a bit big for his environment. Also the eraser was a cute animation, but I bit slow for me (who is very impatient). If you do have time later, it might be fun to come up with a little story for the game also.
Either way good work.