staircase_shaft.lua

local function digcol()
    turtle.digUp()
    turtle.digDown()
end
local function diggo()
    turtle.dig()
    turtle.forward()
end
local r = false
local function rotate()
    if r then turtle.turnLeft()
    else turtle.turnRight() end
end
local function digstep()
    for i=1,2 do
        digcol()
        diggo()
    end
    rotate()
    digcol()
    turtle.down()
    diggo()
    rotate()
    r=not r
end
diggo()
rotate()
r=not r
while true do
   digstep()
end