Starting in a corner seems to be a worst case choice for a random walk on a non-looped grid. I forked it to a) use a random order for starting (and restarting)

Starting in a corner seems to be a worst case choice for a random walk on a non-looped grid. I forked it to a) use a random order for starting (and restarting) http://bl.ocks.org/jix/30e55ae16b99efe94bfc/ab5a84881174512a256136681424d9d6bdadb0d6 http://bl.ocks.org/jix/30e55ae16b99efe94bfc/ab5a84881174512a... and b) start from the center and always restart with the innermost free cell http://bl.ocks.org/jix/30e55ae16b99efe94bfc/aeaced224b45a4136f578a1328cf9bcd46ecb9f6 http://bl.ocks.org/jix/30e55ae16b99efe94bfc/aeaced224b45a413...