0.0.1

local INV_SIZE = 16;
local DIG_LENGTH = 25;

function refuel() if turtle.getFuelLevel() < 5000 then turtle.refuel() end end

function digColumn()
    turtle.dig()
    print("Trying to move forward")
    turtle.forward()
    turtle.digDown()
    turtle.digUp()
end

function digTunnel()
    for i = 0, DIG_LENGTH, 1 do
        digColumn()
    end
end

function forward(squares) for i = 0, squares, 1 do turtle.forward() end end

function digSquare()
    for i = 0, 4, 1 do
        print("Digging tunnel")
        digTunnel()
        turtle.turnRight()
    end
end

function zigZag()
    local nTunnels = math.floor(DIG_LENGTH / 3)
    local direction = 'right'

    for i = 0, nTunnels, 1 do

        if direction == 'right' then
            forward(3)
            turtle.turnRight()
            digTunnel()
            turtle.turnLeft()

            direction = 'left'
        end

        if direction == 'left' then
            forward(3)
            turtle.turnLeft()
            digTunnel()
            turtle.turnRight()

            direction = 'right'
        end
    end

end

function main()
    print("Turtle:")
    print(turtle)
    print("------")
    refuel()
    digSquare()

    zigZag()

end

main()