Good stuff. The environments and visuals looked pretty good, but gameplay feels weird. Not in the sense of controls, but in it's sense of difficulty and pacing. I'd say the biggest culprit is the MP system, since it encourages one thing no matter what: waiting. If you use up your MP, you can restore it but then you have to wait again afterward. If you space out your shots, you ultimately still have to wait since the cooldown length of the MP restore along with slow recharge rates pretty much means you can only shoot 2-3 bullets a second. Enemy layouts seemed to perpetuate this problem as the only thing that really determined difficulty was the number of enemies, so the game only got easier after enemies spawned until more came in. That sense of waiting sucks because it creates a sense of artificial difficulty in the sense that it takes more of your time than your skills.
If you wanted to go the bullet hell direction with this game, enemy bullets should have been slower and do more damage as that encourages much more intentional movement rather than running in circles in order to get into range. Players shouldn't have a resource gate on their bullets unless you do something interesting with it (spells that use HP as a resource that give you MP vice versa, current HP and MP values can be swapped, etc). If you wanted to go more of a spellslinging mage type direction, have spells be simple but interact with each other somehow (maybe have a fireball and an blizzard AoE type thing create a smoke screen that gives players invulnerability when they combine). Take queues from other games that use a similar potion system and have the cooldowns of the restores go down if you are in combat to encourage more aggressive play.
Even with all of that being said, environments are nice, and the musical texture sets up tension nicely. Keep at it!