LS in assembly, 71 bytes

[Whammo]

It could use some refining to add back the features.

code ls
            w  stx,
            1  lda,#
               tax,
         $e8   ldy,#
       $ffbd   jsr,
         $60   lda,#
         $b9   sta,
        $f3d5  jsr,
        $f219  jsr,
         $04   ldy,#
'0' @:  $ee13  jsr,
               dey,
'0' @@         bne,
        $90    lda,
'1' @@         bne,
        $ee13  jsr,
               tax,
        $ee13  jsr,
        $bdcd  jsr,
           bl  lda,#
        $ffd2  jsr,
:-      $ee13  jsr,
        $ffd2  jsr,
-branch        bne,
        $aad7  jsr,
         $02   ldy,#
'0' @@         bne,
'1' @:  $f642  jsr,
        $f6f3  jsr,
            w  ldx,
;code

Ripped off from Michael Steil
https://www.pagetable.com/?p=273