An original idea with a lot of possibilities. Here is my review
The music was rather quiet. I wasnt originally going to put that seeing as it was a royalty free track so there is a chance that track is naturally quiet however i felt i needed to put that point there since the sound effects were too loud next to each other. Having turned up the volume to hear the music lead to a bit of a shock when the sound effect played and nearly split my eardrums.
Art wise i liked the direction for the art however i feel that the grey behind the characters felt a little bland compared to the characters in front however this could just be artistic preference. I did however feel that the characters could have had more variety than just the hair being a different colour however again its a minor nitpick. A final point to note is in the tutorial area, the text overlaps the highscore leaderboard and also has a fair number of spelling mistakes. The very same sentence is hard to read since its mostly obstructed by the various other text from the leaderboard.
The theme was executed rather well in interesting idea and spin on the idea of perfect balance however the gameplay lets it down.
Up until this point these were all minor nit picks that did affect their respective roles depending on how big the nitpicks were compared to the redeeming qualities however with the gameplay, sadly the issues i had were quite bigger.
Aiming for the characters felt way too difficult and strict where you would think your close enough only to find that it still didnt count and when you do hit them, a lot of the time it doesnt work and they still live. This could be improved by having a radius or a minor auto aim to help guide the cursor on top of the enemies when close enough.
The other big issue was the balance not having any UI to tell you where the imbalance is coming from. It does a good job telling you when their is balance but when their isnt the game expects you to instantly know why which is ok when its really obvious such as 3 demons and 1 angel however it borders impossible when theirs say 13 angels and 14 demons, especially in the small time frame you are given to fix the balance before they all fly across the screen at a speed near impossible to catch meanwhile your health is still ticking away at a rate far too fast and not regenerating fast enough to compensate.
Overall, This was a good concept but not such a good execution. It is however, also of note that for what the game is, it makes for an interesting idea and a good attempt at making a game in only 3 days or less. If the above issues were solved, i can imagine this being a fun game to play. I recommend updating the game fixing those issues so you can keep it in a portfolio or learn from the games shortcomings for the next game. You did good and i hope that my critic of your work will help you on your path to being an even more experienced developer in the future and if you decided to, making this game even better! I wish you luck with the rest of the jam and your future as a developer.