For those on steam deck who are confused and would like an easy method to get right into the game. First...
Download the PC version. Extract where you would like. Add the .exe to steam. Go back into game mode. Change the compatibility to Proton Experimental (what I used first) should boot right up, no issue. Control pad is already pre-configured.
Have fun!
Edit: A single crash occurred during the first fortress boss. As soon as I laid the final shot, the boss began to glow bright white and the explode and it crash.
Very well made game, props to the dev and those who helped!