Incredibly fun and addicting. The control is silky smooth, the sprite looks great, and most impressively, the projectile speed is adjusted just right that it requires some aiming but is not terribly difficult. Very polished and well-executed.
To make this game even better, I will highly suggest changing the mana potions to things other than blue (like the green portal?), as there are blue enemies. While at the early stage it is easy to distinguish, later when it becomes more hectic, it is easy to mistake the potions for enemies. Also, it is kinda counter-intuitive that we are supposed to match the elements instead of using the element that counters the enemy's element. Also, some warning (flashes or filters) before you run out of mana (maybe when 1~3 shots left) would be helpful. The screen shake after you run out of mana is not that helpful, especially without other visual cues.
Also, ranked eighth! :D (a leader board for social competitions is very good. Great that you can get that set up in a game jam!) Great game!