Loved the artstyle, and the gameplay was pretty great as well!
I liked the mechanic with throwing the shell and being able to dash with it, but I do feel like you're kind of a sitting duck when you didn't have your shell (no attack and no dash is a bit rough). If anything, I think it'd be good if you could only dash when you don't have your shell, letting you trade defense for speed. Maybe you could make it so pressing the dash button makes you dash into your shell.
I also ended up getting softlocked at some point. I went through a door, and I ended up out of bounds to the left with no way to move anywhere.
All of that said, the core gameplay is solid, and the art & music are amazing. Great stuff!