Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If your opponent controls a monster(s) and you control as many or fewer monsters: Monsters currently on the field gain ATK equal to the combined Levels of all monsters their controller currently controls x 100, until the end of this turn.
--マジカル・スター・イリュージョン
--Magical Star Illusion
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetCondition(s.condition)
	e1:SetTarget(s.target)
	e1:SetOperation(s.activate)
	c:RegisterEffect(e1)
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return Duel.GetFieldGroupCount(tp,LOCATION_MZONE,0)<=Duel.GetFieldGroupCount(tp,0,LOCATION_MZONE)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,1,nil) end
end
function s.activate(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetMatchingGroup(Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,nil)
	local tc=g:GetFirst()
	local val1=Duel.GetMatchingGroup(Card.IsFaceup,tp,LOCATION_MZONE,0,nil):GetSum(Card.GetLevel)*100
	local val2=Duel.GetMatchingGroup(Card.IsFaceup,tp,0,LOCATION_MZONE,nil):GetSum(Card.GetLevel)*100
	for tc in aux.Next(g) do
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_UPDATE_ATTACK)
		if tc:IsControler(tp) then
			e1:SetValue(val1)
		else
			e1:SetValue(val2)
		end
		e1:SetReset(RESETS_STANDARD_PHASE_END)
		tc:RegisterEffect(e1)
	end
end