This was pretty good. I liked the attacking mechanics and the spin thing felt nice.
My only criticism is I could never understand under what conditions did the game allow me to use the spin attack, its like a meter or something and the meter fills as I kill enemies?
Then there is the owl mechanic where you have to find the hidden question mark, its nice to break up the gameplay, but at the same time, its like, it didn't feel like a challenge.
I got as far as I could and then I got to some lava level and then I jumped up a bunch of platforms and then I guess the demo just ends (like out of content).
Overall its amazing. I do feel that there could be some improvements and more enemy diversity and levels and such in the final game if you were to keep going with this.
And a check point system would be great.