anchor: love.system.getPowerInfo
  Gets information about the system's power supply.
  state, percent, seconds = love.system.getPowerInfo()
  state PowerState The basic state of the power supply.
  percent number Percentage of battery life left, between 0 and 100. nil if the value can't be determined or there's no battery.
  seconds number Seconds of battery life left. nil if the value can't be determined or there's no battery.