Game has a lot of potential but for now gameplay is a bit too hard, kicking the ball with LMB is practically useless because trajectory of the ball is unpredictable, hitting those demons is just a bit too difficult. Leaderboard don't seem to work as intended.
There is only ball from the theme, theme is not used well.
Font is out of place, style is not coherent, mixed pixel sizes are the worst, ball and magma have one pixel size and playable character has double pixel size, some mobs have even bigger pixel size. lastly, magma background has too much contrast, it's a bit painful to look at.
I liked the music, I really felt like I'm in the battle.
Conclusion:
Redraw all the assets in one pixel size, make less contrasty background and replace the font, game will look miles better, trust me