How can I get a Settings GUI to save?

Alright thank you! Now how can I make this work for future settings that I add? Do I do the same stuff that you did? What would I need to change?.. for example

script.Parent.MouseButton1Click:Connect(function()
	if game.Lighting.Brightness == 2 then
		game.Lighting.Brightness = 4
		script.Parent.Text = "Bright"
		
	else
		
		if game.Lighting.Brightness == 4 then
			game.Lighting.Brightness = 0
			script.Parent.Text = "Dark"
			
	else
			
		if game.Lighting.Brightness == 0 then
			game.Lighting.Brightness = 2
			script.Parent.Text = "Normal"
			end
		end
	end
end)