I love platformers so I might be a little bit biased here, but in my opinion this is one of the best games that I've played/seen so far.
The main mechanic was really interesting.
The art style was pleasent to the eye.
The background music was nice, altough a little bit repetitive.
And it didn't overstay it's welcome.
Minor things that need improvements:
- I would like to be able to bind multiple keys to an action, sometimes I needed to switch around while enemies were heading towards me and that was a little bit frustrating. (for example A and D to jump)
- I found 2 bugs, one where you can create infinite + images as long as you don't place them on a valid surface and the last level had a "next level" button that didn't work.