Enemies who look like squares rotated by 45 degrees, are very confusing, they make you question whether "that square" is a drop or a mob making it harder to decide whether a position is safe or not
I know they're probably temporary sprites, but they really should look like something else even as WiP, especially the tiny ones.
In menu where you pick next stage, when picking the buff symbol (dunno what it's called) it lacks some sort of confirmation. There were many times when I clicked it, and then waited 1 second before realizing "oh I need to pick the next stage now".
There's nothing to indicate that something happened, like a sound or whatever, initially I thought it's a bug that locks the game, because I thought the stage is not loading.
Getting new guns feels really exciting because there's so much variety.
I think enemy bullets should disappear after killing all enemies. Getting killed after finishing the level would be very frustrating, and I feel like it doesn't add anything to the game. The possibility of surviving by the skin of your teeth, because you killed last monster 0.1s before the bullet hit you is much more interesting.
Really appreciate little details like, horned guys having unhappy faces when getting hit, old blood changing color or the satisfying vibration of high hp mobs when you're frying them with a laser.
When you press Tab to see info about your gun, and pick next stage and get level up window - the info about a gun obscures upgrades and you can't turn it off with a Tab.