Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If you control no monsters, you can Normal Summon this card without Tributing. Once per turn, during your opponent's Standby Phase: This card's ATK becomes double its current ATK until the end of this turn.
--デプス・シャーク
--Depth Shark
local s,id=GetID()
function s.initial_effect(c)
	--summon with no tribute
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetProperty(EFFECT_FLAG_UNCOPYABLE)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_SUMMON_PROC)
	e1:SetCondition(s.ntcon)
	c:RegisterEffect(e1)
	--atk
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,1))
	e2:SetCategory(CATEGORY_ATKCHANGE)
	e2:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_F)
	e2:SetCode(EVENT_PHASE|PHASE_STANDBY)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCountLimit(1)
	e2:SetCondition(s.atkcon)
	e2:SetOperation(s.atkop)
	c:RegisterEffect(e2)
end
function s.ntcon(e,c,minc)
	if c==nil then return true end
	return minc==0 and c:GetLevel()>4 and Duel.GetLocationCount(c:GetControler(),LOCATION_MZONE)>0
		and Duel.GetFieldGroupCount(c:GetControler(),LOCATION_MZONE,0)==0
end
function s.atkcon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.IsTurnPlayer(1-tp)
end
function s.atkop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if c:IsFaceup() and c:IsRelateToEffect(e) then
		local e1=Effect.CreateEffect(c)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_SET_ATTACK_FINAL)
		e1:SetValue(c:GetAttack()*2)
		e1:SetReset(RESETS_STANDARD_DISABLE_PHASE_END)
		c:RegisterEffect(e1)
	end
end