This artwork is BEAUTIFUL!!! The animation, music, and magical environment are very well done.
One of the biggest things I think would help this game is to have a zoom feature to zoom the camera in and out. I feel like this would be fairly easy to implement and extremely beneficial to the player. I would just walk into the enemy and get hit with very little room to know that they're there. The zoom feature would solve this issue.
I'm guessing since it's unfinished, once the player defeats all the enemies with the potion it just sends them to the game over screen. That's a bit confusing to the player if they don't know that this game is incomplete, maybe just create a copy of the game over screen but with text that says something like "You did it! You saved the magical school from the army of monsters!" or "End of demo" just so the player knows that they've reached the end.
If I'm being extremely critical, then an animation on the star below the player would be really cool, especially if it was initially just the player but then once they get the potion the star gets added below them and glows/expands when they use the potion attack.
Overall incredible artwork and I'd be interested in playing the full version if you decide to finish it! :)