os thing (uncommented)

local options = {'Shutdown', 'Reboot'}
local menuopen = false

while true do
    term.setBackgroundColor(colors.black)
    term.clear()

    local w,h = term.getSize()

    paintutils.drawLine(1, h, w, h, colors.blue)

    term.setTextColor(colors.black)
    term.setBackgroundColor(colors.lime)
    term.setCursorPos(1, h)
    write('Start')

    if menuopen then
        term.setBackgroundColor(colors.white)
        term.setTextColor(colors.black)

        for i=1, #options do
            term.setCursorPos(1, h - i)
            print(options[i])
        end
    end

    local event, button, mousex, mousey = os.pullEvent('mouse_click')
    if mousey == h and mousex >= 1 and mousex <= 5 then
        menuopen = not menuopen
    end
end