-- get arguments

local tArgs = { ... }
if #tArgs ~= 1 then
	print( "Usage: basicTunnel; <Tunnel Length divided by 2>" )
	return
end

local tunnelLength = tonumber( tArgs[1] )
if tunnelLength < 1 then
	print( "Tunnel Length must be positive!" )
	return
end

-- function to tunnel 1x3 directly in front moving into new space

local function digInFront ()

	if turtle.detect() then
		if turtle.dig() then
			turtle.suckDown()
		end
	end

	turtle.forward()

	if turtle.detectUp() then
		if turtle.digUp() then
			turtle.suckDown()
		end
	end

	if turtle.detectDown() then
		if turtle.digDown() then
			turtle.suckDown()
		end
	end

	turtle.back()
end

-- program start

local done = false

while not done do
	for n = 0, tunnelLength do

		digInFront()
		turtle.turnRight()
		digInFront()
		digInFront()
		turtle.turnLeft()

		digInFront()
		turtle.turnLeft()
		digInFront()
		digInFront()
		turtle.turnRight()
	end
	done = true
end