Minecraft Mining Turtle

local error1 = "No Fuel!"
local error2 = "Tool Broken!"
local tunnellenght = 3
local spacebetween = 2
local tunnels = 10
local backway = tunnels*(spacebetween+1)

for i=1, tunnels do

    for i=1, tunnellenght do

        while turtle.detect()==true do
            turtle.dig()
            os.sleep(0.5)
        end

        turtle.forward()

    end

    turtle.turnLeft()
    turtle.turnLeft()

    for i=1, tunnellenght do

        turtle.forward()

    end

    turtle.turnRight()
    turtle.dig()
    turtle.forward()
    turtle.digDown()

    for i=1, spacebetween do

        while turtle.detect()==true do
            turtle.dig()
            os.sleep(0.5)
        end

        turtle.forward()
        turtle.digDown()

    end

    turtle.turnRight()
    turtle.refuel()

end

turtle.turnRight()

for i=1, backway do

    while turtle.detect()==true do

        turtle.dig()
        turtle.digDown()

    end

    turtle.forward()

end