I had feared the icons would look like pickups. So when you run out of ammo you reroll a new weapon and the icon over your character is the reroll animation selecting a new powerup. When an enemy dies it rolls a buff as well so it also shows an icon over where they died. The boss icon is a permanent buff (if you max out all his buffs and kill him you win) while the grunt enemies get a temporary buff for that life and basically exist to annoy you. The boss icons definitely look like powerups though since they're buff icons for the boss itself (+boss hp, + boss speed, + boss shoot pattern, + enemy spawn). I'm glad you still enjoyed the game though!