-- 逆ピラミッド

local num = 10

local lnum=0

turtle.select(1)

for i = 1,10 do
  turtle.up()
end

-- ここから

for j =-1*num ,num do
  for i = -1*num,num do
    if (num)^2 >= j^2 + i^2 then
      if (num)^2 <= (j+1)^2 + (i+1)^2 then
			  turtle.placeDown()

      end
    end

  turtle.forward()
  end

  for i = -1*num,num do
    turtle.back()
  end

  turtle.turnRight()
  turtle.forward()
  turtle.turnLeft()

end