1x1 dig down

y=0


function checkFuel()
    if turtle.getFuelLevel() < 100 then
        turtle.select(1)
        turtle.refuel(1)
    end
end

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

function dig()
    if turtle.down() == true then
        checkFuel()
        turtle.digDown()
        y=y+1
    else
        up()
        os.exit()
    end
end




checkFuel()
turtle.digDown()

while true do
    dig()
end