Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
During your Standby Phase, inflict 300 damage to your opponent for each monster they control.
--黒魔導師クラン
--Ebon Magician Curran
local s,id=GetID()
function s.initial_effect(c)
	--damage
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_DAMAGE)
	e1:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_F)
	e1:SetProperty(EFFECT_FLAG_PLAYER_TARGET)
	e1:SetCode(EVENT_PHASE|PHASE_STANDBY)
	e1:SetRange(LOCATION_MZONE)
	e1:SetCountLimit(1)
	e1:SetCondition(s.condition)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return tp==Duel.GetTurnPlayer()
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	local ct=Duel.GetFieldGroupCount(tp,0,LOCATION_MZONE)
	Duel.SetTargetPlayer(1-tp)
	Duel.SetOperationInfo(0,CATEGORY_DAMAGE,nil,0,1-tp,ct*300)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local p=Duel.GetChainInfo(0,CHAININFO_TARGET_PLAYER)
	local ct=Duel.GetFieldGroupCount(tp,0,LOCATION_MZONE)
	Duel.Damage(p,ct*300,REASON_EFFECT)
end