Solid take on a relatively common idea. I like how the size panels affected the boxes too, that was clever. Everything was put together in ways that used the mechanics interestingly and they were taught well.
Enter/Middle Click are both very awkward and weird controls for grabbing boxes, though. Z or E would've made a lot more sense. There was also a lot of issues where the boxes could clip you into the terrain which could be ironed out.
Despite those two issues, the game was good! Great job.