The onDead method from drone enemies

drone.lua

local function onDead(world, drone)
  Signal.emit('enemyKilled', drone)
  local viralAmount = (drone.health.damage.viral or 0) / drone.health.max
  if viralAmount >= 0.5 then
    drone.animation.currentName = 'dead'
    drone.body.fx = 50
    drone.invoke = {
      onInvoke = 'doLoot'
    }
    particles:viralSparks(drone)
    world:addEntity(drone)
  else
    drone.removeMe = true
    boom:small(util.entityMiddle(drone))
  end
  Sound:droneHurt()
end