menu

term.clear()
term.setCursorPos(1,1)
selected = 1
running = true

a = {
  {"Option 1"},
  {"Option 2"},
  {"Option 3"}
}

function printCentered(str)
  local x, y = term.getCursorPos()
  local maxX, maxY = term.getSize()
  term.setCursorPos(maxX/2-string.len(str)/2,y)
  write(str)
  term.setCursorPos(1,y+1)
end

function selector(array)
  local event, param = os.pullEvent("key")
  if event == "key" then
    if param == 200 and selected > 1 then
      selected = selected - 1
    elseif param == 208 and selected < table.getn(array) then
      selected = selected + 1
    elseif param == 28 then
      array[selected][2]()
    end
  end
end

function display(array)
  for i = 1,table.getn(array) do
    if i == selected then
      printCentered("["..array[i][1].."]")
    else
      printCentered(array[i][1])
    end
  end
end

while running do
  term.clear()
  term.setCursorPos(1,8)
  display(a)
  selector(a)
end