Nice Puzzle game ! The mechanics are really cool and fit the theme nicely.
I only wish there was an undo button to cancel your last move. I soft-locked myself quite a few time in the last levels with the boxes & had to restart the level (which can be a bit frustrating)
I would also have prefered using the arrow keys (usually wasd is for when you need to use the mouse at the same time)
appart from that. very solid game. great job :)