Pretty good puzzle game. I'm very happy you decided to just increase the die value by one instead of doing the standard rolling mechanic, but probably my favourite design decision is the multi-push mechanic. There's probably still some puzzle potential left to be explored here, but the levels feel pretty good already and I don't quite see it being expandable into a "full" puzzle game, so this is currently in a pretty good spot I think.
I thought the game was a bit on the easy side, but I do think I have above average expertise with sokoban-like puzzles, so if you want to appeal to a broader audience, the difficulty is probably fine. Difficulty curve seemed mostly fine. I felt like level 7 was a bit annoying, as it didn't really teach any new mechanics and getting the boxes into their spots felt more tedious than fun.
Also, props for all the nice convenience features! Undo is great, as is grid mode, though that one could be a little more prominent. I personally don't ever see myself turning off squiggliness, but it's still a nice feature to have. Only thing I would suggest is to also add some sort of checkerboard pattern, which helps a lot with parity puzzles like this.
Graphics are minimalist but nice, though I would personally prefer a slightly more "relatable" main character. Sound was okay, music I wasn't a huge fan of, but that comes down to personal preference, I think.