I remember this game from way back when! It's still super fun and I'll be wishlisting it.
My only critique is that on a ultra-wide monitor, some of the UI breaks. The main gameplay is cut off to the center part, but the items & gun expand out to the "dead zone" beyond it. This is most noticeable when leveling up- the rune selection covers up everything but I can still see my first two guns on the bottom left.
Also, why am I not allowed to see my guns during rune selection? Would be nice to know if I have rifles for Rifle Enthusiast.