selectedSlot = 0
lastturn = 0
turn = {1=turtle.turnLeft(),2 = turtle.turnRight()}
while true do
    while turtle.forward() do
        turtle.digDown()
        while not turtle.placeDown() do
            selectedSlot = selectedSlot % 16 + 1
            turtle.select(selectedSlot)
        end
    end
    while turtle.getFuelLevel() == 0 do
        turtle.select(1)
        turtle.refuel(64)
    end
    if turtle.detect() then
        turn[lastturn]
        turtle.forward()
        turn[lastturn]
        lastturn = lastturn % 2 + 1
    end
end