Not horrible, everything basically works from a control standpoint, but there's not really any strategy here. The enemy hitboxes are so large and stack on top of each other too quickly. I had to try to miss. Really the issue was that those hitboxes on the enemies' Y-axes are not rigged independently of the Y-axis on the field of play. This means that there's only aiming in a general direction: even if an enemy is "lower" on the playing field the shot will probably hit that enemy first. It takes away quite a bit of target prioritization decisions from the player. Basically they just shoot the closest thing. They rarely have a choice otherwise.
Spell cooldown is often too slow to make it reliable, when you need it to be reliable. Health and speed upgrades made much more the difference here than mana. Health was nice, but if you couldn't kill the enemy in the front of the line fast enough all the others would swarm and kill... even that was a tertiary upgrade priority after upgrading power and speed and the weapon. Become strong enough with the basic firing pattern and one could simply point the mouse in one of two directions and watch the game play itself.
I was thinking from the opening graphic that I'd be juggling three different characters at the same time, different firing types and patterns, swapping characters out if their spells and mana were all used up, with more enemy variety and bosses that had interesting unique attack patterns. That's the game I was hoping to play when I clicked on this. What you have here is functional, but is underwhelming compared even to other games of this type.