while true do
os.pullEvent = os.pullEventRaw

local w,h = term.getSize()
local solarState = "OFF"

function printCentered( y,s )
   local x = math.floor((w - string.len(s)) / 2)
   term.setCursorPos(x,y)
   term.clearLine()
   term.write( s )
end

local nOption = 1

local function drawMenu()
   term.clear()
term.setCursorPos(1,2)

   term.setCursorPos(w-11,1)
   if nOption == 1 then
        term.write("Solar power")
   elseif nOption == 2 then
        term.write("Exit")
else
end

end

--GUI
term.clear()
local function drawFrontend()
   printCentered( math.floor(h/2) - 3, "")
   printCentered( math.floor(h/2) - 2, "Start Menu" )
   printCentered( math.floor(h/2) - 1, "")
   printCentered( math.floor(h/2) + 0, ((nOption == 1) and "[ Solar power ]") or "Solar power" )
   printCentered( math.floor(h/2) + 1, ((nOption == 2) and "[ Exit ]") or "Exit" )
   printCentered( math.floor(h/2) + 4, "")
end

--Display
drawMenu()
drawFrontend()

while true do
 local e,p = os.pullEvent()
 if e == "key" then
  local key = p
  if key == 17 or key == 200 then

   if nOption > 1 then
    nOption = nOption - 1
    drawMenu()
    drawFrontend()
   end
  elseif key == 31 or key == 208 then
  if nOption < 4 then
  nOption = nOption + 1
  drawMenu()
  drawFrontend()
end
elseif key == 28 then

break
end
end
end
term.clear()

--Conditions
if nOption  == 1 then
        if solarState == "OFF" then
                solarState = "ON"
                rs.setBundledOutput("back", colors.yellow )
                drawMenu()
                drawFrontend()
        else
                solarState = "OFF"
                rs.setBundledOutput("back", colors.yellow )
                drawMenu()
                drawFrontend()
        end
else
        os.shutdown()
end
end