self = script.Parent

gui = script
while not gui:IsA("ScreenGui") do
    gui = gui.Parent
    if gui.Name == "PlayerGui" then
        error()
    end
end

local scale = 0.8

function updateSelf()
    local h = gui.AbsoluteSize.Y*scale
    script.Parent.Size = UDim2.new(0,h,0,h)
    script.Parent.Position = UDim2.new(0.5,h/-2,0.5,h/-2)
end

updateSelf()
gui.Changed:connect(updateSelf)