Spawning Enemys Indicator

Hello so you maybe know the game Brotato its an Idle game where random enemys spawn around you.If they gonna spawn there is always a little indicator (a little x) where you can see that they spawn and I was wondering how you can do that in roblox studio
In this clip you can see what I mean

so if you know how to do something like this pls let me know

btw if you need that here is my script for spawning enemys at random positions

local enemyspawn = script.Parent
local rs = game:GetService("ReplicatedStorage")
local event = rs:WaitForChild("Events")
local enemys = rs:WaitForChild("Enemys")
local startgameevent = event:WaitForChild("StartGame")

	while true do 
		local randomenemy = enemys:GetChildren()[math.random(1,#enemys:GetChildren())]:Clone()

		randomenemy.Parent = game.Workspace.Enemys
	randomenemy:SetPrimaryPartCFrame( - (enemyspawn.Size.X/2), enemyspawn.Position.X +(enemyspawn.Size.X/2) ) ,3,math.random(enemyspawn.Position.Z - (enemyspawn.Size.Z/2), enemyspawn.Position.Z + (enemyspawn.Size.Z/2) ))))

Look into BillboardGuis.

You could attach one to an invisible part in workspace, then use a tween to change its transparency (maybe with a “Bounce” type to get the in-and-out effect).

Connect to the Completed method of that tween, and inside that connection you’d actually spawn your enemy.