I love how you made a tutorial, as well as the simple SFX / Music, though I do suggest a change in font would be nice (more pixel-ly to fit the theme, seemed out of place.) Also another suggestion would be to add a DontDestroyOnLoad onto the music so it doesn't abruptly transition. Also I don't get how sometimes my combined creature just poofs into nothing.
I do now though realize when filling a bar, a cool effect occurs, maybe that could've been explained better in the tutorial