Thanks for your thorough review! Exactly what I need for further development.
The "overdone" post processing only applies to being near a portal. As they only spawn after collecting all shards in the level, I thought I'd give players a hint where to go to, should they collect all. But yeah, will definitely need some more polish!
Art is the only thing I can't do myself, so I had to get good at working with those kinds of standard assets haha. And it's URP without lightning though, so just the post-processing stack and a colour palette.