Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Once per turn: You can send any number of cards from your hand to the GY; place 1 Balloon Counter on this card for each card sent to the GY. All monsters your opponent controls lose 300 ATK for each Balloon Counter on this card.
--ワンダー・バルーン
--Wonder Balloons
local s,id=GetID()
function s.initial_effect(c)
	c:EnableCounterPermit(0x32)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	c:RegisterEffect(e1)
	--counter
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_COUNTER)
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetRange(LOCATION_SZONE)
	e2:SetCountLimit(1)
	e2:SetCost(s.cost)
	e2:SetTarget(s.target)
	e2:SetOperation(s.operation)
	c:RegisterEffect(e2)
	--atk down
	local e3=Effect.CreateEffect(c)
	e3:SetType(EFFECT_TYPE_FIELD)
	e3:SetCode(EFFECT_UPDATE_ATTACK)
	e3:SetRange(LOCATION_SZONE)
	e3:SetTargetRange(0,LOCATION_MZONE)
	e3:SetValue(s.atkval)
	c:RegisterEffect(e3)
end
s.counter_place_list={0x32}
function s.atkval(e,c)
	return e:GetHandler():GetCounter(0x32)*-300
end
function s.cost(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(Card.IsAbleToGraveAsCost,tp,LOCATION_HAND,0,1,nil) end
	local ct=Duel.DiscardHand(tp,Card.IsAbleToGraveAsCost,1,60,REASON_COST)
	e:SetLabel(ct)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	Duel.SetOperationInfo(0,CATEGORY_COUNTER,nil,e:GetLabel(),0,0x32)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp,chk)
	local c=e:GetHandler()
	if c:IsRelateToEffect(e) and c:IsFaceup() then
		c:AddCounter(0x32,e:GetLabel())
	end
end