Rewrite the rule Location as follows:

There is a string variable named “Location” which is privately tracked by the Gridmaster for each Runner and is either a blank string or contains the identification of a Cell, defaulting to a blank string. At any time, a Runner whose Location is a blank string may privately request the Gridmaster to set their Location to a specific Cell. The Gridmaster should process these requests in the order in which they were received. If no other Runner has this Cell in their Location at the time the message is processed, the Gridmaster sets the Location of the Runner to the requested Cell and replies with an acknowledgement of the request. Otherwise, the Gridmaster replies that the Cell is taken.

There is a string variable called “Spoor” which is privately tracked by the Gridmaster for each Runner. A Runner’s Spoor is either a blank string or contains the identification of up to three Cells. Whenever a Runner’s Location changes, its former value is added to that Runner’s Spoor at its leftmost point. If this would result in that Runner’s Spoor containing a reference to more than three Cells then the rightmost value is removed from that Runner’s Spoor and is instead set as that Runner’s Ping.

A Runner’s Ping is a publicly tracked variable which may only hold Cell references, and which defaults to blank.

At any time, a Runner may privately request a Glance around their current Location from the Gridmaster, to which the Gridmaster replies with that Runner’s current Location, their full Spoor, and the names of all Runners (if any) who are Nearby that Runner.