I can't believe that square root not one shotting x^2 went over my head! I'm reasonably confident the x's are splitting into their exponent value, but if your combo is high enough you can kill their spawns as it's happening so it seems more random since you can pierce more and more enemies with each exponent.
I definitely considered having more types of expressions and operators as the game went on. If I revisit the project and introduce trigonometry and calculus.
Thanks for playing and for the feedback. This is my first project as a dev!
(edited for missing words)