Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can Special Summon this card by removing from play any 2 Rock-Type monsters in your Graveyard. During your Standby Phase, remove from play 1 Rock-Type monster in your Graveyard, or send this card to the Graveyard. Halve the ATK and DEF of any monster that battles with this card.
--地球巨人 ガイア・プレート
--Gaia Plate the Earth Giant
local s,id=GetID()
function s.initial_effect(c)
	--special summon
	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)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
	--atk/def down
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_FIELD)
	e2:SetCode(EFFECT_SET_ATTACK_FINAL)
	e2:SetRange(LOCATION_MZONE)
	e2:SetTargetRange(0,LOCATION_MZONE)
	e2:SetCondition(s.adcon)
	e2:SetTarget(s.adtg)
	e2:SetValue(s.atkval)
	c:RegisterEffect(e2)
	local e3=e2:Clone()
	e3:SetCode(EFFECT_SET_DEFENSE_FINAL)
	e3:SetValue(s.defval)
	c:RegisterEffect(e3)
	--maintain
	local e4=Effect.CreateEffect(c)
	e4:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_CONTINUOUS)
	e4:SetProperty(EFFECT_FLAG_CANNOT_DISABLE+EFFECT_FLAG_UNCOPYABLE)
	e4:SetCode(EVENT_PHASE|PHASE_STANDBY)
	e4:SetRange(LOCATION_MZONE)
	e4:SetCountLimit(1)
	e4:SetCondition(s.mtcon)
	e4:SetOperation(s.mtop)
	c:RegisterEffect(e4)
end
function s.filter(c)
	return c:IsRace(RACE_ROCK) and c:IsAbleToRemoveAsCost() and aux.SpElimFilter(c,true)
end
function s.spcon(e,c)
	if c==nil then return true end
	local tp=c:GetControler()
	local rg=Duel.GetMatchingGroup(s.filter,tp,LOCATION_MZONE|LOCATION_GRAVE,0,nil)
	return Duel.GetLocationCount(tp,LOCATION_MZONE)>-2 and #rg>1 and aux.SelectUnselectGroup(rg,e,tp,2,2,aux.ChkfMMZ(1),0)
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk,c)
	local rg=Duel.GetMatchingGroup(s.filter,tp,LOCATION_MZONE|LOCATION_GRAVE,0,nil)
	local g=aux.SelectUnselectGroup(rg,e,tp,2,2,aux.ChkfMMZ(1),1,tp,HINTMSG_REMOVE,nil,nil,true)
	if #g>0 then
		g:KeepAlive()
		e:SetLabelObject(g)
		return true
	end
	return false
end
function s.spop(e,tp,eg,ep,ev,re,r,rp,c)
	local g=e:GetLabelObject()
	if not g then return end
	Duel.Remove(g,POS_FACEUP,REASON_COST)
	g:DeleteGroup()
end
function s.adcon(e)
	return Duel.IsPhase(PHASE_DAMAGE_CAL) and e:GetHandler():GetBattleTarget()
end
function s.adtg(e,c)
	return c==e:GetHandler():GetBattleTarget()
end
function s.atkval(e,c)
	return c:GetAttack()/2
end
function s.defval(e,c)
	return c:GetDefense()/2
end
function s.mtcon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.IsTurnPlayer(tp)
end
function s.mtop(e,tp,eg,ep,ev,re,r,rp)
	if Duel.IsExistingMatchingCard(s.filter,tp,LOCATION_MZONE|LOCATION_GRAVE,0,1,nil)
		and Duel.SelectYesNo(tp,aux.Stringid(id,0)) then
		Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_REMOVE)
		local g=Duel.SelectMatchingCard(tp,s.filter,tp,LOCATION_MZONE|LOCATION_GRAVE,0,1,1,nil)
		Duel.Remove(g,POS_FACEUP,REASON_COST)
	else
		Duel.SendtoGrave(e:GetHandler(),REASON_RULE)
	end
end