Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If it is not the first turn of the Duel and there are no cards on the field, you can Normal Summon this card without Tributing. You can destroy all Field Spell Cards on the field. This card cannot attack the turn you activate this effect.
--グラヴィティ・ベヒモス
--Gravity Behemoth
local s,id=GetID()
function s.initial_effect(c)
	--Normal summon it with no tributes
	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)
	--Destroy all field spells on the field
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,1))
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetCategory(CATEGORY_DESTROY)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCountLimit(1)
	e2:SetCost(s.descost)
	e2:SetTarget(s.destg)
	e2:SetOperation(s.desop)
	c:RegisterEffect(e2)
end
function s.ntcon(e,c,minc)
	if c==nil then return Duel.GetTurnCount()~=1 end
	return minc==0 and c:GetLevel()>4 and Duel.GetLocationCount(c:GetControler(),LOCATION_MZONE)>0
		and Duel.GetFieldGroupCount(c:GetControler(),LOCATION_ONFIELD,LOCATION_ONFIELD)==0
end
function s.descost(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return e:GetHandler():GetAttackAnnouncedCount()==0 end
	--Cannot attack this turn
	local e1=Effect.CreateEffect(e:GetHandler())
	e1:SetDescription(3206)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_CANNOT_ATTACK)
	e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE+EFFECT_FLAG_OATH+EFFECT_FLAG_CLIENT_HINT)
	e1:SetReset(RESETS_STANDARD_PHASE_END)
	e:GetHandler():RegisterEffect(e1)
end
function s.destg(e,tp,eg,ep,ev,re,r,rp,chk)
	local g=Duel.GetMatchingGroup(aux.TRUE,0,LOCATION_FZONE,LOCATION_FZONE,nil)
	if chk==0 then return #g>0 end
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,g,#g,0,0)
end
function s.desop(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetMatchingGroup(aux.TRUE,0,LOCATION_FZONE,LOCATION_FZONE,nil)
	if #g>0 then
		Duel.Destroy(g,REASON_EFFECT)
	end
end