v                      pos in 0,0, depth in 1,0, aim in 2,0
>00p10p20p>#;~:'f-#v_$&:00g+00p     v@,a.*g01g00;
                   >'d-#v_$&20g+20pv>20g*10g+10pv
                        >&20g\-20p v            <
          ^         ;,a.g01.g00; ~ << # we do not forget to strip the \n from the input