Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Target any number of face-up monsters your opponent controls, up to the number of face-up Spell Cards you control; change those monsters to face-down Defense Position.
--EMショーダウン
--Performapal Show Down
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetCategory(CATEGORY_POSITION)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetHintTiming(TIMING_BATTLE_PHASE,TIMINGS_CHECK_MONSTER|TIMING_BATTLE_PHASE)
	e1:SetTarget(s.target)
	e1:SetOperation(s.activate)
	c:RegisterEffect(e1)
end
function s.cfilter(c)
	return c:IsFaceup() and c:IsSpell()
end
function s.filter(c)
	return c:IsFaceup() and c:IsCanTurnSet()
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	local sc=Duel.GetMatchingGroupCount(s.cfilter,tp,LOCATION_ONFIELD,0,nil)
	if chkc then return chkc:IsControler(1-tp) and chkc:IsLocation(LOCATION_MZONE) and s.filter(chkc) end
	if chk==0 then return sc>0 and Duel.IsExistingTarget(s.filter,tp,0,LOCATION_MZONE,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_FACEUP)
	local g=Duel.SelectTarget(tp,s.filter,tp,0,LOCATION_MZONE,1,sc,nil)
	Duel.SetOperationInfo(0,CATEGORY_POSITION,g,#g,0,0)
end
function s.activate(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetTargetCards(e)
	if #g>0 then
		Duel.ChangePosition(g,POS_FACEDOWN_DEFENSE)
	end
end