Short and sweet! I thought the level titles were actually a great way at hinting to the player, it helped a lot on some of the later levels. It's *just* difficult enough to make you feel smart, but never enough to the point of frustration.
If this is getting a full release, I think it's worth considering nonlinear level progression; giving the player multiple levels to tackle means they're more likely to try another instead of quitting entirely when they get stuck.
I also appreciate your restraint in seeing how far you could push designing levels with just 2 types of buttons, crates, and on/off doors. You wrung a lot of variety out of that! If I could add one new object, I think a tile that rotates the character would expand on the game's core idea of positioning and character manipulation.
Anyways, great work. Wishlisted!