>pink blobs are immune to bullets
>think they're invincible at first
>nope, just have to use the sword
The sword is the same button as the gun, by the way. So if you want to kill a boss with the sword, you need to get suicidally close to make sure that you don't accidentally fire a bullet (which is what happened on the first boss in this run). It's funny when the simplest things add a bit of depth to a game.