Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Your opponent cannot select a face-down Defense Position monster as an attack target.
--ヒエラコスフィンクス
--Hieracosphinx
local s,id=GetID()
function s.initial_effect(c)
	--at limit
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_FIELD)
	e1:SetCode(EFFECT_CANNOT_SELECT_BATTLE_TARGET)
	e1:SetRange(LOCATION_MZONE)
	e1:SetTargetRange(0,LOCATION_MZONE)
	e1:SetValue(s.atlimit)
	c:RegisterEffect(e1)
end
function s.atlimit(e,c)
	return c:IsPosition(POS_FACEDOWN_DEFENSE)
end