Thank you! I did want to make a ton of new enemies but I figured I didn't have enough time to really polish them if I did!
The background entity is just 3 sprites layered on top of each other constantly rotating (in different directions and speeds) then I put on a "fire" shader on it so it moves like flames and tweaked the parameters.
The entity that you fight is made out of only particles.
The real magic that ties it all together is putting the stretch to viewport and the scale to integer so it looks like an actual made sprite!