Okay first thing I notice when I start: the music. This music is incredibly good, gives a really energetic vibe. Art is pretty good as well.
Gameplay is interesting, often just found myself staying at the fountain and moving one crystal around while spamming fireballs. Maybe ramp up the difficulty more over time while making upgrades more impactful so the player has more incentive to keep every crystal alive? It was decently replayable, although of course some more maps or weapons would have helped. In terms of controls I'd rather have had the fireball on right click so I didn't have to bend my hand around as much.
In short, the core concept for the game is great. This definitely has potential.