function mydig()
	if turtle.detect() then
		turtle.dig()
	end
	turtle.forward()
end

function mydigdown()
	if turtle.detectDown() then
		turtle.digDown()
	end
	turtle.down()
end

function fuelcheck()
    if turtle.getFuelLevel() < 1 then
	    turtle.refuel()
	end
end

function strip(y)
  	-- From center dig to y
	for i=0,y do
	  mydig()
	end
	for i=0,y do
	  turtle.back()
	end
	turtle.turnRight()
	mydig()
	turtle.turnLeft()
end

function octet ( radius )

  x = 0
  y = radius
  p = 1 - radius

  i = 0
  lower_octet = {}

  while( x < y ) do

    if( p < 0 ) then
      p = p + (2*x+2) + 1
      x = x + 1
    else
      p = p + (2*x+2) + 1 - (2*y-2)
      x = x + 1
      y = y - 1
    end

    print("(" .. x .. "," .. y .. ")")
    strip(y)

    lower_octet[i] = { y, x }
    i = i+1
  end
  print("-------");

  i = i - 1

  while( i >= 0 ) do
    print("(" .. lower_octet[i][1] .. "," .. lower_octet[i][2] .. ")")
	strip(lower_octet[i][2])
    i = i - 1
  end
end

radius = 6
fuelcheck()

octet( radius )