Looks like fun, I like the background art style and it looks really responsive. The pixel particles on death feel out of place with the rest of the art style though. I agree with — on the game length, unless it's just a demo (or on itch you could mark in development, with promise of more levels or features.)
I'm wondering if you want to add a sense of urgency w/ some kind of timer (in gameplay, e.g. flooding, impeding doom from creature or something company or via simple timer per level, with carry over time, e.g. like Marble Madness.)
Perhaps try out making the fireballs in the same color scheme as the layout and player (w/ perhaps more effects to make it obvious they are deadly). See what that looks like, I think it will look 'clean'.
Nice work, looking forward to seeing more.