local function find_energy_cube()
  local cube_names = {"Ultimate Energy Cube", "Elite Energy Cube", "Advanced Energy Cube", "Basic Energy Cube"}
  local cube = nil
  for cube_name in cube_names do
    cube = peripheral.find(cube_name)
    if cube != nil then
      break
    end
  end
  return cube
end

local cube = find_energy_cube()

if cube == nil then
  print("No energy cube found!")
  exit()
end

local threshold_percent = 90
local max_energy = cube.getMaxEnergy()
local stored_energy = max_energy
local stored_percent = stored_energy/max_energy

local cable_side = "bottom"
local color_separator = colors.red

while true do
  -- Update values
  stored_energy = max_energy
  stored_percent = stored_energy/max_energy

  -- Change state accordingly
  if stored_percent > threshold_percent then
    redstone.setBundledOutput(cable_side, color_separator)
  else
    redstone.setBundledOutput(cable_side, 0)
  end
end