Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can discard 1 card to the GY, then target 1 monster your opponent controls with DEF less than or equal to this card's ATK; destroy that target.
--魔轟神ガルバス
--Fabled Gallabas
local s,id=GetID()
function s.initial_effect(c)
	--destroy
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_DESTROY)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetType(EFFECT_TYPE_IGNITION)
	e1:SetRange(LOCATION_MZONE)
	e1:SetCost(s.cost)
	e1:SetTarget(s.tg)
	e1:SetOperation(s.op)
	c:RegisterEffect(e1)
end
function s.costfilter(c)
	return c:IsDiscardable() and c:IsAbleToGraveAsCost()
end
function s.cost(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(s.costfilter,tp,LOCATION_HAND,0,1,nil) end
	Duel.DiscardHand(tp,s.costfilter,1,1,REASON_DISCARD|REASON_COST)
end
function s.filter(c,atk)
	return c:IsFaceup() and c:IsDefenseBelow(atk)
end
function s.tg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	local c=e:GetHandler()
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsControler(1-tp) and s.filter(chkc,c:GetAttack()) end
	if chk==0 then return Duel.IsExistingTarget(s.filter,tp,0,LOCATION_MZONE,1,nil,c:GetAttack()) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_DESTROY)
	local g=Duel.SelectTarget(tp,s.filter,tp,0,LOCATION_MZONE,1,1,nil,c:GetAttack())
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,g,1,0,0)
end
function s.op(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	local c=e:GetHandler()
	if c:IsFaceup() and c:IsRelateToEffect(e) and tc:IsFaceup() and tc:IsRelateToEffect(e) and tc:IsDefenseBelow(c:GetAttack()) then
		Duel.Destroy(tc,REASON_EFFECT)
	end
end