No you're right there's only one boss in the jam version, planning to add more in future though. Also yeah the shotgun ended up being a bit overtuned, I did want it to be stronger than the blaster up close but I think the DPS is something like 6x as much if you land all your shots so definitely needs a rebalance.
Glad you liked the art, took me a while to get it done but I'm happy with how it turned out.