Minecraft Turtle: Pyramid

--[[
    2013 (c) psychedelixx
    Minecraft Turtle: Pyramid
    2013-06-14

    desc

    Usage:
    - use turtle and type "label set <name>"
      (to give your turtle an unique name so it remembers its programs)
    - type "pastebin get <code> pyramid"
    - type "pyramid <length>" (32 for full 4x4x64 chest)
--]]

slot = 0

function move()
    if turtle.getFuelLevel() < 5 then
        turtle.refuel()
    end
    if turtle.getItemCount(slot%16+1)==0 then
    slot = slot+1
    turtle.select(slot%16+1)
    end
    turtle.placeDown()
    turtle.forward()
end

local args = { ... }
if #args < 1 then
    print( "Usage: pyramid <length> [32 for full 4x4x64 chest]" )
    error()
end
x = tonumber(args[1])
odd = x%2==1

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!")

    start = true
    dir = 1
    turtle.up()
    repeat
        if dir%4 == 1 and not start then
            move()
            turtle.up()
        end
        block = 1
        if odd and x==1 then
            move()
            x=x-1
            else repeat
            move()
            block = block+1
        until block >= x end
        turtle.turnRight()
        dir = dir+1
        if dir%4 == 1 or dir%4 == 0 then x = x-1 end
        if start then start = false end
    until x<=0
end