Twin-stick shooters aren't my cup of tea but I played for about an hour and unlocked the 2nd character but only got about 4-5 stages (excluding the Nexus) deep at most. But what I did play was solid. It might be how drop chances are weighted or I just got unlucky with my relatively few runs but the ballus & ice rune seemed to drop fairly frequently--aside from those two you've got a solid weapon variety & rune variety. The power-up pricing seems to be just about perfect right & I only really started to have more money than that after I got the compounding-interest bonus. The spinning reload animation is nice, and the destructible-ish terrain (I'm thinking of walls & pillars in particular) is also very cool. One time I destroyed a wall and a bunch of cavernous rooms were revealed--VERY COOL!
Also I'm playing on a POS laptop (think 2011 notebook gpu) and didn't encounter framerate issues--it was always consistent and no stutters. So great job optimizing performace!