Hello! I just played the Project Feline demo (0.9.3). I wanted to share my thoughts on the fun I had, in case the feedback is useful to the developer.
My favorite experience in the demo was getting lost in the Interchange (Explore mode). I found myself in a flow state, continually using movement skills to orient myself and understand the level's layout. The scattered collectibles served as markers of spots I hadn't reached yet, ensuring I never got too lost. It was exciting, having the freedom to go anywhere, and using that freedom to get myself lost, and then gradually become un-lost as I crisscrossed the level and mentally mapped it...
Every time I crossed a passageway or threshold and saw familiar space on the other side, I felt rewarded with more understanding of the level's interconnections. Every time I crossed and saw unfamiliar space, I felt rewarded with additional space to explore.
To Raymond: I don't know whether this is still something you're deliberating on, but I'll say that I prefer the semi-open exploration design of the Interchange over the linear level designs. When it comes to games focused on fun movement, I think exploration-heavy levels work well for 3D games, while linear/technical levels may be more suited to 2D platformers.
I hope this perspective helps, and good luck with continued development!