As a developer who also submitted a sokoban puzzle game I just want to say how impressed I am. Your system is extremely novel and unique, and truly lead to some innovative and fun puzzles. I cannot stress this enough, this is a phenomenal game \( ^o^)/
however...
SPOILERS BELOW, DON'T READ ON IF YOU PLAN TO PLAY THE GAME YOURSELF
My only suggestion is in regards to level design. In level 7 for example, there's a lot of open space, two boxes, and a door. The solution I found is to have the two boxes collide against each other so neither is able to undo. This solution isn't explicitly taught in any of the other levels, which is unfortunate because it's a very cool mechanic that stems from the rules of the game, but I stumbled across it completely by accident. Seeing such a wide open space, I had assumed the solution would be similar to the solution of level 3, which was a false assumption brought on by the ambiguous level design. Which brings me back to the suggestion I was going to make: creating a puzzle with less space can make it easier for the player to see when they are doing something wrong. For a really good example of a sokoban game and puzzle design you can look at Patrick's Parabox (the game I drew inspiration from while making my entry for the jam). In Patrick's Parabox, mechanics and strategies are first introduced in smaller "training-wheels" levels, then the levels get larger and the puzzles stem from the player trying to figure out how to apply the mechanics they just learned.
That's just my idea on the topic, but if your puzzle design philosophy is different than mine, I completely understand. In the case that I'm just one person who struggled where no one else did, then I apologize for making you read all that. To reiterate one final time: your game is super duper awesome, I'm not trying to hate or anything, just trying to give some puzzle design advice :)