I would say my biggest regret was developing some background props that I didn't end up using (lights and things like that). I like to challenge myself and make all the assets during the jam, to have a theme that fits the mechanic, and I think I've accomplished that. But when something goes unused because I didn't have time to implement it, that's when creating that asset feels like a waste of time, which I could've spent designing an extra level, or refining enemy behavior. But all in all, I'm very happy with how the game turned out.