TextButton Popup GUi not appearing?

(This is the first time I've ever scripted something for a GUi, keep that in mind.) I'm trying to make a TextButton that makes a frame popup when clicked, and have it disappear if clicked again, how do I do this? In my current script, I inserted this LocalScript inside the TextButton. (I also apologize if this code block looks horrendous, I'm trying to get used to this new editor.)

 menuopen = game.StarterGui.TPStuff.FullMenu.Visible
thegui = game.StarterGui.TPStuff
  script.Parent.Mouse1Click:connect(function()
if menuopen == false then
thegui.FullMenu.Visible = true
elseif menuopen == true then
thegui.FullMenu.Visible = false
end
end)