4 item menu

term.setBackgroundColor(colors.gray)
term.setCursorPos(1, 1)
term.clear()
local react = peripheral.wrap("back")
local termX, termY = term.getSize()
local selector = 1
local menu_options = {
  [1] = { text = "Reactor ON/OFF Toggle", color = colors.blue },
  [2] = { text = "Reactor Fuel Level", color = colors.black },
  [3] = { text = "Reactor Power Level", color = colors.orange },
  [4] = { text = "Reactor Fuel Usage (Consumed Last Tick)", color = colors.cyan }
}

local function menuDraw(selected)
  local yPos = (termY - #menu_options) / 2
  for index, data in pairs(menu_options) do
    menu_options[index].bounds = {
      x1 = termX / 2 - (#data.text + 4) / 2,
      x2 = termX / 2 + (#data.text + 4) / 2,
      y = yPos
    }
    term.setTextColor(data.color)
    term.setCursorPos(data.bounds.x1, data.bounds.y)
    term.write(" " .. data.text .. " ")
    yPos = yPos + 1
  end
end

local function checkClick(x, y)
  for index, data in pairs(menu_options) do
    if x >= data.bounds.x1 and x <= data.bounds.x2 and y == data.bounds.y then
      return index
    end
  end
  return false
end

while true do
  menuDraw(selector)
  local e = { os.pullEvent() }
  if e[1] == "mouse_click" then
    local value = checkClick(e[3], e[4])
    if value then
      selector = value
      break
    end
  end
end

if selector == 1 then
  if react.getActive() == true then
    react.setActive(false)
    os.reboot()
  elseif react.getActive() == false then
    react.setActive(true)
    os.reboot()
  end
elseif selector == 2 then
  write(react.getFuelAmount() .. "/" .. react.getFuelAmountMax())
  sleep(2)
  os.reboot()
elseif selector == 3 then
  write(react.getEnergyStored() .. "/10,000,000")
  sleep(2)
  os.reboot()
elseif selector == 4 then
  write(tostring(react.getFuelConsumedLastTick()))
  sleep(2)
  os.reboot()
end