Good and interesting concept for a bullet haven game type, but there is plenty of room to grow if you want to follow up with this game.
- First, as kevin pointed out, the game could be more enjoyable if shooting can be toggled to automated or hold to fire, and ROF upgrade.
- Second, substantial and diverse upgrade is what gives this genre insane replayability, and you can use references as both inspiration/explanation to put in all types of upgrade that would make the game even more fun and theme-related.
- Third, enemies are still bare-bone and their hitboxes stacks to a unified blob if you kite them enough, which both raise and lower the difficulty in a very boring way in later stage. Give them collision body between themselves so they won't stack and explode all at once and give them more types (shape/size/etc.). Also, I have a little idea for elite enemies, as you can use arithmetic operations as enchantments: "plus" increase their size and add more number to them if they are hit by explosion, "multiply" doubles surrounding enemies when killed, "minus" has reduced size and explosion radius, "divide" divides into 2 smaller enemies when killed and only deal half explosion damage, etc.