Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can only activate this card's effect while you control a face-up "Koa'ki Meiru" monster. Once per turn, during your Standby Phase, if your opponent controls more monsters than you do, you can destroy a number of cards your opponent controls so that your opponent will control the same number of cards as you control monsters.
--コア・ブラスト
--Core Blast
local s,id=GetID()
function s.initial_effect(c)
	--activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetHintTiming(0,TIMING_END_PHASE)
	c:RegisterEffect(e1)
	--maintain
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_O)
	e2:SetCode(EVENT_PHASE|PHASE_STANDBY)
	e2:SetRange(LOCATION_SZONE)
	e2:SetCountLimit(1)
	e2:SetCondition(s.descon)
	e2:SetTarget(s.destg)
	e2:SetOperation(s.desop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_KOAKI_MEIRU}
function s.descon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.IsTurnPlayer(tp)
		and Duel.GetFieldGroupCount(tp,LOCATION_MZONE,0)<Duel.GetFieldGroupCount(tp,0,LOCATION_MZONE)
		and Duel.IsExistingMatchingCard(aux.FaceupFilter(Card.IsSetCard,SET_KOAKI_MEIRU),tp,LOCATION_MZONE,0,1,nil)
end
function s.destg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	local g=Duel.GetMatchingGroup(aux.TRUE,tp,0,LOCATION_ONFIELD,nil)
	local ct=Duel.GetFieldGroupCount(tp,0,LOCATION_MZONE)-Duel.GetFieldGroupCount(tp,LOCATION_MZONE,0)
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,g,ct,0,0)
end
function s.desop(e,tp,eg,ep,ev,re,r,rp)
	if not e:GetHandler():IsRelateToEffect(e) then return end
	local g=Duel.GetMatchingGroup(aux.TRUE,tp,0,LOCATION_ONFIELD,nil)
	local ct=#g-Duel.GetFieldGroupCount(tp,LOCATION_MZONE,0)
	if ct<=0 then return end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_DESTROY)
	local dg=g:Select(tp,ct,ct,nil)
	Duel.Destroy(dg,REASON_EFFECT)
end