Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Cannot declare an attack unless your opponent activated a card or effect this turn.
--ナチュル・スパイダーファング
--Naturia Spiderfang
local s,id=GetID()
function s.initial_effect(c)
	--atk limit
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_CANNOT_ATTACK_ANNOUNCE)
	e1:SetCondition(s.atkcon)
	c:RegisterEffect(e1)
	Duel.AddCustomActivityCounter(id,ACTIVITY_CHAIN,aux.FALSE)
end
function s.atkcon(e)
	return Duel.GetCustomActivityCount(id,1-e:GetHandlerPlayer(),ACTIVITY_CHAIN)==0
end