This is increadible for a "Newbie". The concept is awesome, I am pretty syre with a little bit of polish in the art and maybe changing the controlers (I got used to it but it is weird to move and attack and dash with those buttons), this game could have a way bigger feeling. I loved the idea, the environment looks great, it was definelly a BOSS over there. Music is not boring and once you get used to the gameplay style you actually want more!
Great job on your project, it was really great!
Also one thing I forgot, instead of text tutorial, you could implement a map or a scene where the player will be able to test all the features instead just dropping him in the field and fight the boss, but those are only small features that could be done in the future!