Build a Pyramid with a building turtle in the MineCraft mod ComputerCraft

pyramid.lua

b = 0 --bricks laid
w = 0 --wall number
h = 200 --height of the structure in layers
i = 0 --current number layers
x = 64--how wide the base should be 
n = 1 --selection number for inv

function start()
	turtle.up()
end
function sel()
	if turtle.getItemCount(n) <1 then--check to see if we are out of material
		n = n+1
	end
	if n > 16 then --if we are done the last item slot
		n = 1 --switch back to slot one
		while turtle.getItemCount(1) <1 do --if there is nothing in slot one ask user to refill
			print ('please reload, by filling slot one last')
			sleep(1)
		end
	end
	turtle.select(n)--change slot
end




function buildlayer()
	if w == 0 then
		x = x -1
	end
	while w < 4 do --while we have not built 4 walls yet
		while b < x do

			sel()
			turtle.placeDown()
			turtle.forward()--build the wall
			b = b + 1
		end
		while b == x do
			turtle.turnLeft()--turn so we can build the next wall
			w = w+1
			b = 0
		end
		if w == 3 then
			x = x-1
		end
	end
	
	while w == 4 do
		turtle.placeDown()
		turtle.up()--move up so we can start another layer
		
		turtle.forward()
		w = 0
	end
end
start()
while i < h do--while we have not reached our intended height
	buildlayer()
	i = i+1
end