Pull. A consumer that wants a value sends a pull to the address it holds. A producer answers by shipping itself over; an unfinished computation records the reader and starts working.
Fire. When a producer reaches its consumer the rule fires right there: fresh agents take free slots (the dying consumer's own slot first), and anything the rule hands to someone else travels as a message.
No locks. Every value has exactly one reader, so every request about a value comes from one place, and a tile settles races by handling one event at a time.
Demand and drop. Nothing runs until something asks for it. An eraser sends a drop instead: a producer is erased where it stands, and a computation nobody can read any more is cancelled.
Room. When a tile is full, a rewrite docks and follows the free-space field (toggle space) to the nearest tile with enough room. Running out of room is reported, never guessed around.
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