I think your core mechanic of attracting boxes absolutely has promise (as another commenter mentioned, the 'jumping over the box' puzzle was really cool). However, if you want to have a trial and error game, you need to make getting back into the action as simple and fast as possible. The issue isn't that the respawn is slow, it's that the movement is. I think that increasing movement speed and decreasing empty space in your levels would go a long way to making this game phenomenal if you want to work on it post-jam. Not only does it reduce filler, puzzles are generally best when presented as compact as possible (easier to see everything at play, gives the player a feeling of 'wow, the solution should be right in front of me'). It's a jam game - you don't need more than a few minutes of good gameplay.
Overall, good job!