while true do
  local seed = math.randomseed(10)
  local time = math.random(600)
  local timer = os.startTimer(time)
  local sleep = math.random(8)
  while true do
    local event, result = os.pullEvent()
    if event == "timer" and timer ==result then
      redstone.setOutput("left", true)
      os.sleep(sleep)
      redstone.setOutput("left", false)
      break
    end
  end
end