User blog comment:Wythagoras/SuperJedi's X function/@comment-4224897-20141113192733/@comment-10429372-20150430184001

Actually, I will post my ideas here, and you may want to try it yourself: Define for every state the function f(a,b,c,d,e), where a is the rightmost part of tape, b is leftmost part, c is current symbol. d is the current place, and e is on which tape. a and b are just decimal integers, so to change symbol, add or subtract 10^d.