Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If your opponent controls 2 or more monsters and you control no monsters, you can Special Summon this card (from your hand). If this card is Normal or Special Summoned: You can target 1 Level 4 or lower "Superheavy Samurai" monster in your Graveyard, except "Superheavy Samurai Scales"; Special Summon it in Defense Position. You can only use this effect of "Superheavy Samurai Scales" once per turn.
--超重武者テンB－N
--Superheavy Samurai Scales
local s,id=GetID()
function s.initial_effect(c)
	--spsummon
	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)
	c:RegisterEffect(e1)
	--spsummon
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_O)
	e2:SetCode(EVENT_SUMMON_SUCCESS)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_DAMAGE_STEP+EFFECT_FLAG_DELAY)
	e2:SetCountLimit(1,id)
	e2:SetTarget(s.sptg)
	e2:SetOperation(s.spop)
	c:RegisterEffect(e2)
	local e3=e2:Clone()
	e3:SetCode(EVENT_SPSUMMON_SUCCESS)
	c:RegisterEffect(e3)
end
s.listed_series={SET_SUPERHEAVY_SAMURAI}
s.listed_names={id}
function s.spcon(e,c)
	if c==nil then return true end
	return Duel.GetFieldGroupCount(c:GetControler(),LOCATION_MZONE,0)==0
		and Duel.GetFieldGroupCount(c:GetControler(),0,LOCATION_MZONE)>1
		and Duel.GetLocationCount(c:GetControler(),LOCATION_MZONE)>0
end
function s.filter(c,e,tp)
	return c:IsSetCard(SET_SUPERHEAVY_SAMURAI) and c:IsLevelBelow(4) and not c:IsCode(id) and c:IsCanBeSpecialSummoned(e,0,tp,false,false,POS_FACEUP_DEFENSE)
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_GRAVE) and chkc:IsControler(tp) and s.filter(chkc,e,tp) end
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
		and Duel.IsExistingTarget(s.filter,tp,LOCATION_GRAVE,0,1,nil,e,tp) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
	local g=Duel.SelectTarget(tp,s.filter,tp,LOCATION_GRAVE,0,1,1,nil,e,tp)
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,g,1,0,0)
end
function s.spop(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) then
		Duel.SpecialSummon(tc,0,tp,tp,false,false,POS_FACEUP_DEFENSE)
	end
end