Lighter

x,y,z=1,1,0
dir=0

function Forward()
	while not turtle.forward() do
		turtle.attack()
	end
	if (dir%2)==0 then y=y+1-(dir%4)
	else x=x+2-(dir%4)
	end
end

function Up()
	while not turtle.up() do
		turtle.attackUp()
	end
	z=z+1
end

function Down()
	while not turtle.down() do
		turtle.attackDown()
	end
	z=z-1
end

function Right()
	turtle.turnRight()
	dir=(dir-1)%4
end

function Left()
	turtle.turnLeft()
	dir=(dir+1)%4
end

function SelectTorch()
	for i=1,16 do
		local data=turtle.getItemDetail(i)
		if data and data.name=="minecraft:torch" then
			turtle.select(i)
			break
		end
	end
end

function SelectCobble()
	for i=1,16 do
		local data=turtle.getItemDetail(i)
		if data and data.name=="minecraft:cobblestone" then
			turtle.select(i)
			break
		end
	end
end

function PlaceTorch()
	local success,data=turtle.inspect()
	if success and data.name=="minecraft:cobblestone" then
	else
		SelectCobble()
		turtle.place()
		Up()
		SelectTorch()
		turtle.place()
		Down()
	end
end

function Column()
	for i=1,100 do
		if turtle.detect() then break end
		Forward()
		if (y%4)==0 then
			Left()
			PlaceTorch()
			Right()
		end
	end
	Right() Right()
	while y>1 do Forward() end
	Right() Right()
end



while true do
	Left()
	if turtle.detect() then
		Right() Right()
		while x>1 do Forward() end
		Left()
	else
		for n=1,100 do
			Forward()
			if x%3==1 then
				Right()
				Column()
				Left()
				if turtle.detect() then
					Right()
					break
				end
			end
		end
	end
end