clarified rules in viz 1

_posts/2018-11-12-viz-1.md

@@ -25,11 +25,15 @@ This visualization follows a few simple rules:
 * Any point can only be occupied by a single node. A point may be alive (filled)
   or dead (empty).
 
-* Every tick each live point picks from 0 to N new points to spawn, where N is
+* On every tick each live point picks from 0 to N new points to spawn, where N is
   the number of empty adjacent points to it. If it picks 0, it becomes dead.
 
 * Each line indicates the parent of a point. Lines have an arbitrary lifetime of
-  a few ticks. When a dead point's line is cleaned up so is it.
+  a few ticks, and occupy the points they connect (so new points may not spawn
+  on top of a line).
+
+* When a dead point has no lines it is cleaned up, and its point is no longer
+  occupied.
 
 The resulting behavior is somewhere between [Conway's Game of
 Life](https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life) and white noise.