Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
2 monsters You cannot Link Summon this card unless you have at least 3 more cards in your Extra Deck than your opponent's.
--リンクルベル
--Linkerbell
--
local s,id=GetID()
function s.initial_effect(c)
	c:EnableReviveLimit()
	--link summon
	Link.AddProcedure(c,nil,2,2)
	--splimit
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_SPSUMMON_COST)
	e1:SetCost(s.spcost)
	c:RegisterEffect(e1)
end
function s.spcost(e,c,tp,st)
	if (st&SUMMON_TYPE_LINK)~=SUMMON_TYPE_LINK then return true end
	return Duel.GetFieldGroupCount(tp,LOCATION_EXTRA,0)-Duel.GetFieldGroupCount(tp,0,LOCATION_EXTRA)>=3
end