Whoa, I am so impressed with this!
The design is top notch, the sound design of the box scraping is a nice touch, the sounds are relaxing, the gameplay is smooth and intuitive, and the fact you managed to create a level editor for it is impressive. Really great work! The timer to enforce people focus on the effectivity of their game play is also great.
Did I miss music in the game? Is is there? If not, that would be the only thing I would advise to add, aside from that I can imagine people playing this on desktop or mobile, great work!