thanks very much for your feedback! i'm working on a large update at the moment and i've neglected to update the demo... there's lots of new stuff, but i think a lot of your feedback is still relevant. it's still needs some work, but i think i might be able to share the next version soon-ish.
yeah i agree it would be cool to add more interactive mechanics, like picking up stuff/ koopa shells. i'll think about it! i feel like i'm running out of buttons and the main character doesn't have arms, so it's tough to figure this one out...
the money doesn't do anything, you can think of them like celeste strawberries. in the current working version of the game i ditched this idea.
i've made some performance improvements and lots of other fixes since this version, so hopefully issues like fps dips and weird tile gaps will be resolved.
the file size was really large because i was using .wav files for the songs. i've since converted them to .oggs. it's about half the size now.