A fun little take on a boss battle, I like that it was something different other than slinging a sword at a monster or something, the boiler actually made the whole thing with its' attacks make a lot of sense. I did try to walk up to the monster to whack it before realizing I'd activated some kind of throw thing by accident somewhere in the process, it took me a bit to figure it out but once I did it was a fun challenge. The movement is a little tricky, maybe it's just me and my tendency to spam click in an attempt to smoothly navigate somewhere in games like RTSes, but I kept having the poor mechanic die just on the edge of a steam tile.
Good job overall, I really appreciate how polished the game is. The boss is adorable!