The gameplay loop of catching lightning to generate mana that allows for attacks is a very interesting concept with a lot of potential. With some adjustments I think this could make for a fairly addictive minigame.
First I want to talk about the art. The characters and enemies use a very simple pixel style which can work in a vacuum, however they clash pretty harshly with the much more detailed background tiles.
I really like the rain effect you layer over the top. I think it fits well with the characters and gives the scene a lot of life, but like with the characters, it clashes a bit with the background.
The UI throughout the game does have a fun style to it, but the very round sleek designs of the various bars and text is also different from both the characters and background, which leads to the game being less visually cohesive. Using pixel fonts and custom UI with pixel designs can help alleviate some of these issues.
The biggest issue with the visuals is that there is a lack of feedback for the player regarding certain actions. Things like taking or dealing damage don’t show any animation. By adding a hurt animation, or by simply flashing the character or enemy red/white, you could convey that information much more clearly.
In a similar vein, the enemy projectiles are very small and almost certainly won’t be noticed by players on their first few attempts. These should likely be larger, but could also have some kind of particle to help them stand out.
As for the audio, I think the background rain and thunder helps set the tone of your game. However I would still suggest layering music on top of the sounds that are present, as a looping song will generally create a more fun environment for the player. If music isn’t your thing, I suggest the Kevin MacLeod library of songs. You can pretty much always find royalty free music that fits your needs here: https://incompetech.com/music/royalty-free/music.html
And as a very small note, there's a brief stop/start for the rain when changing scenes. When the music/ambience aren't changing between scenes it may be helpful to keep the sound playing rather than letting it restart (This can be done really easily by adding a script to make your music object a “Singleton”).
Moving on to the sound effects, I think sounds that are all present are quite detailed and do a good job helping the player with timing their actions. However you can never have too many sound effects for player feedback. Adding various sounds for after the player hits does a “Lightning Absorption" could help inform them of how close they were. Other sounds for enemies landing hits on the player or the range enemies shooting could also help the player stay informed of how they are doing.
Next I want to talk about the gameplay. The core loop of catching lightning and then using that mana to attack creates an interesting back and forth where the player can stay away from the enemies until they need to jump in and get mana. This creates a really natural feeling of risk/reward which works well for this game.
The variety of spells to use is also a nice touch, however it’s hard to find a point where there's enough enemies on screen to get a lot of value from the larger attacks (Or perhaps the basic spell is just too good?).
That being said, the lack of enemy numbers may just be related to the roadblock that's stopping me from reaching later waves. Around wave 3 the ranged enemies become more common, and their homing attacks are guaranteed to hit the player (As far as I can tell). Not sure if that was intentional, but I would suggest making the projectiles larger, but removing the homing effect. This would still let projectiles be a threat, but not something that guarantees damage just because the enemy spawned. Based on other comments, this seems to be where most people got stuck.
My last note has to do with enemy spawns. It’s common for enemies to spawn in the arena, where they can be on top of the player and get a free hit. This is hard for the player to deal with, so its would be cleaner if they only appeared offscreen and walked into frame.
Overall, this is an intriguing concept with potential to become a very addicting game with a few tweaks. I apologize if this review was a bit much, but I'm doing this to all the games from this jam as I think critiques help us grow.