I did procrastinate about this, but I finally refactored my code from the jam ;). It's now more extendable and ready for further development. Unfortunately I now have merge conflicts in my repository, so I'm gonna have to learn how to resolve these. I'll upload the demo tomorrow if all goes well.
On the visual side of things, I've increased contrast throughout the game and added post-processing to more scenes. Here's the improved difficulty select screen as an example:
