Minecraft Turtle - 3 Field Stripmining

-- MC Turtle Stripmining Program
----------------------------------------------------------

-- Variables
----------------------------------------------------------
glength = 0
gwidth = 0
cnt = 0
scnt = 1

-- Dialoge
----------------------------------------------------------
write("Length: ")
glength = tonumber(read())

write("Width: ")
gwidth = tonumber(read())

-- Function: refill
----------------------------------------------------------
function refill()
  for idx = 1,16 do
    turtle.select(idx)
    turtle.refuel()
  end
    turtle.select(1)
end

-- Function: torch (Places a Torch)
----------------------------------------------------------
function torch(mode)
  turtle.select(16)

  if mode == 2 then
    turtle.place()
  else
    turtle.placeDown()
  end

  turtle.select(1)
end

-- Function: turn180 (Turn 180 Deg)
----------------------------------------------------------
function turn180()
  turtle.turnRight()
  turtle.turnRight()
end

-- Function: step (Makes one digging step forward)
----------------------------------------------------------
function step(mode)

  if mode == 2 then

    while turtle.detectUp() do
      turtle.digUp()
      sleep(0.5)
    end

    while turtle.detectDown() do
      turtle.digDown()
    end

  end

  while (not turtle.forward()) do
    turtle.dig()
  end

  while turtle.detectDown() do
    turtle.digDown()
  end

  while turtle.detectUp() do
    turtle.digUp()
    sleep(0.5)
  end


end

-- Function: halfstrip (Digs one Strip side)
----------------------------------------------------------
function halfstrip(lwidth)
  flag = false

  lcnt = 1
  while (lcnt < lwidth) do
    step(2)
    lcnt = lcnt + 1
  end
  lcnt = 1
  while (lcnt < lwidth) do
    while (not turtle.back()) do
      sleep(0.5)
    end
    if (not flag) then
      torch(2)
      flag = true
    end
    lcnt = lcnt + 1
  end
end

-- Function: strip (Digs the complete Strip)
----------------------------------------------------------
function strip(gwidth)
    turtle.turnRight()
      halfstrip(gwidth)
    turtle.turnLeft()

    turtle.turnLeft()
      halfstrip(gwidth)
    turtle.turnRight()
end


-- MAIN FUNCTION
----------------------------------------------------------
while (cnt<glength) do

  if turtle.getFuelLevel() < 1 then
    refill()
  end
  if turtle.getFuelLevel() < 1 then
    write ("Not enough fuel!")
    return
  end

  step(1)

  if (scnt >= 3) then
    strip(gwidth)
    torch(1)
    scnt = 0
  else
    scnt = scnt + 1
  end

  cnt = cnt + 1

end

write ("Mission completed.")
return