Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
This card's effect changes depending on the number of DARK monsters in your Graveyard. ● 1 or fewer: This card loses 400 ATK. ● 2 to 4: This card gains 400 ATK. ● 5 or more: You can send this card to the Graveyard to destroy all face-down monsters your opponent controls.
--ダーク・アサシン
--Dark Hunter
local s,id=GetID()
function s.initial_effect(c)
	--destroy
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetProperty(EFFECT_FLAG_SINGLE_RANGE)
	e1:SetRange(LOCATION_MZONE)
	e1:SetValue(s.atkval)
	c:RegisterEffect(e1)
	--destroy
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_DESTROY)
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCondition(s.condition)
	e2:SetCost(Cost.SelfTribute)
	e2:SetTarget(s.target)
	e2:SetOperation(s.operation)
	c:RegisterEffect(e2)
end
function s.atkval(e,c)
	local ct=Duel.GetMatchingGroupCount(Card.IsAttribute,c:GetControler(),LOCATION_GRAVE,0,nil,ATTRIBUTE_DARK)
	if ct<=1 then return -400
	elseif ct<=4 then return 400
	else return 0 end
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return not e:GetHandler():IsDisabled() and Duel.IsExistingMatchingCard(Card.IsAttribute,tp,LOCATION_GRAVE,0,5,nil,ATTRIBUTE_DARK)
end
function s.filter(c)
	return c:IsFacedown()
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(s.filter,tp,0,LOCATION_MZONE,1,nil) end
	local g=Duel.GetMatchingGroup(s.filter,tp,0,LOCATION_MZONE,nil)
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,g,#g,0,0)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetMatchingGroup(s.filter,tp,0,LOCATION_MZONE,nil)
	Duel.Destroy(g,REASON_EFFECT)
end