Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
2 Level 5 WATER monsters During either player's turn: You can detach 1 Xyz Material from this card, then target 1 face-up monster on the field; its ATK becomes half its current ATK until the end of your turn.
--No.94 極氷姫クリスタル・ゼロ
--Number 94: Crystalzero
local s,id=GetID()
function s.initial_effect(c)
	--xyz summon
	Xyz.AddProcedure(c,aux.FilterBoolFunctionEx(Card.IsAttribute,ATTRIBUTE_WATER),5,2)
	c:EnableReviveLimit()
	--atk down
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_ATKCHANGE)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_DAMAGE_STEP)
	e1:SetType(EFFECT_TYPE_QUICK_O)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetRange(LOCATION_MZONE)
	e1:SetHintTiming(TIMING_DAMAGE_STEP)
	e1:SetCondition(aux.StatChangeDamageStepCondition)
	e1:SetCost(Cost.DetachFromSelf(1))
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
s.xyz_number=94
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsFaceup() end
	if chk==0 then return Duel.IsExistingTarget(Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_FACEUP)
	Duel.SelectTarget(tp,Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,1,1,nil)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) and tc:IsFaceup() then
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_SET_ATTACK_FINAL)
		e1:SetValue(tc:GetAttack()/2)
		if Duel.IsTurnPlayer(1-tp) then
			e1:SetReset(RESETS_STANDARD_PHASE_END,2)
		else
			e1:SetReset(RESETS_STANDARD_PHASE_END,1)
		end
		tc:RegisterEffect(e1)
	end
end