Minecraft Turtle: Rescue stairs

--[[
    2013 (c) psychedelixx
    Minecraft Turtle: Rescue Stairs
    2013-05-24

    Digs a 2x2 rescue stair straight up.

    Usage:
    - use turtle and type "label set <name>"
      (to give your turtle an unique name so it remembers its programs)
    - type "pastebin get qL9nfNc0 rescue"
    - place solid blocks in slot 16 (lower right corner)
    - type "rescue"
--]]

function move()
        if turtle.getFuelLevel() < 2 then
                turtle.refuel()
        end
        if fillGround and not turtle.detectDown() then
                turtle.select(16)
                turtle.placeDown()
        end

        while not turtle.forward() do
                turtle.dig()
        end
        repeat
                turtle.digUp()
        until not turtle.detectUp()
end

if turtle.getFuelLevel() == 0 then
    turtle.refuel()
end

if turtle.getFuelLevel() == 0 then
    print("I need fuel!")
else
    print("======== 2013 (c) psychedelixx ========")
    print("Let's go!")

    hollow = 0
    move()
    while turtle.getFuelLevel() > 0 and hollow < 6 do
        print("")
        print("Fuel: " .. turtle.getFuelLevel())

        move()
        turtle.up()
        if not turtle.detectUp() then
            hollow = hollow + 1
        end
        turtle.digUp()
        turtle.turnLeft()
    end
    repeat
        turtle.down()
        hollow = hollow - 1
    until hollow <=0
end