--by exechack.cc 

hook.Add("PostRenderVGUI", "gpusaver", function()
	if system.HasFocus() then
		return
	end
	local W, H = ScrW() * 0.5, ScrH() * 0.5
	cam.Start({
		type = "2D"
	})
	surface.SetDrawColor(0, 0, 0)
	surface.DrawRect(0, 0, W * 2, H * 2)
	cam.End2D()
end)