Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If your opponent controls a face-up Xyz Monster, you can Special Summon this card (from your hand). When you do: Target 1 monster your opponent controls; that monster loses 300 ATK.
--パクバグ
--Bite Bug
local s,id=GetID()
function s.initial_effect(c)
	--special summon
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_FIELD)
	e1:SetCode(EFFECT_SPSUMMON_PROC)
	e1:SetProperty(EFFECT_FLAG_UNCOPYABLE)
	e1:SetRange(LOCATION_HAND)
	e1:SetCondition(s.spcon)
	e1:SetValue(1)
	c:RegisterEffect(e1)
	--atkchange
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e2:SetCode(EVENT_SPSUMMON_SUCCESS)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e2:SetCondition(s.atkcon)
	e2:SetTarget(s.atktg)
	e2:SetOperation(s.atkop)
	c:RegisterEffect(e2)
end
function s.filter(c)
	return c:IsFaceup() and c:IsType(TYPE_XYZ)
end
function s.spcon(e,c)
	if c==nil then return true end
	return Duel.GetLocationCount(c:GetControler(),LOCATION_MZONE)>0 and
		Duel.IsExistingMatchingCard(s.filter,c:GetControler(),0,LOCATION_MZONE,1,nil)
end
function s.atkcon(e,tp,eg,ep,ev,re,r,rp)
	return e:GetHandler():GetSummonType()==SUMMON_TYPE_SPECIAL+1
end
function s.atktg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsControler(1-tp) and chkc:IsFaceup() end
	if chk==0 then return true end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_TARGET)
	Duel.SelectTarget(tp,Card.IsFaceup,tp,0,LOCATION_MZONE,1,1,nil)
end
function s.atkop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	local tc=Duel.GetFirstTarget()
	if tc and tc:IsRelateToEffect(e) and tc:IsFaceup() then
		local e1=Effect.CreateEffect(c)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_UPDATE_ATTACK)
		e1:SetValue(-300)
		e1:SetReset(RESET_EVENT|RESETS_STANDARD)
		tc:RegisterEffect(e1)
	end
end