I like the minimalism in the art. Honestly even in full games I prefer simplicity over details.
And here pixel art is implemented on a high level - respect +
Also, one thing is to come up with a mechanic and the other is to make levels for this mechanic. And in my opinion those levels are great. Short, simple but smart and support the mechanic.
I wish there would be some music and sounds. And it can be a full game with more levels.