It took me a long while to reach the goal, but once I found the route, optimization wasn't difficult. Really unique puzzle. Definitely one of my favorites now.
I had a wrong idea about something, so I was always two off (for 137). When I was quite certain, that the path I have, is optimized and can't be improved, only then did I consider, how on earth it could be done differently and then I saw, what unnecessary thing I was doing here, and right after I managed to turn the box full. ;)
