I like the idea, but it doesn't feel like the player has much agency. Bouncing off the box to change direction is inconsistent and I often ended up breaking out, which was frustrating.
It would help to give the player some control over their movement beyond rotating and scaling the box. A few abilities like a speed boost or a predictable way to change direction would help a lot. If you do that and fix the inconsistencies in the box collisions, this could be an interesting game. Feels kind of like Undertale combat, and could be pretty fun with some changes.
That said, congrats on completing the jam. Keep it up!