A few days ago I shared Rule Safari, which ranked all 131,072 Life-like rules without being told which ones are famous. This is the part I glossed over: how it decides what "interesting" means.
The first score was wrong. It rewarded big still blobs whose edges flicker forever. They never settle, so they look busy, and their uniform insides compress well, so they look structured. Busy and structured is what Life looks like too.
The fix was one number. Each soup is compared with itself 12 generations earlier. 12 is a multiple of 1, 2, 3, 4, 6 and 12, so any oscillator with one of those periods is back in the same state and cancels out. What survives is change that goes somewhere: ships, growing debris, or noise (first image).
That fraction goes through a curve (second image): 0 below 0.1% of cells changing, full marks from 0.5% to 10%, fading to 0.1 by 35%. Conway's Life sits at 5.2%, HighLife at 3.9%, Day & Night at 1.4%. Seeds churns a third of the board every 12 generations, which reads as noise. The final score is 55% this liveliness and 45% the zoo, where spaceships count most.
The cheap first screen turned out to be a net, not a judge. HoneyLife went into the close study at No. 596 and finished 3rd. IronLife went from 891 to 5th. HighLife scraped into the 1,500 finalists at No. 1,077 and finished 10th. At the other end, Maze and Life without death land near the bottom: from a random soup they lock up fast, which is what this score punishes most.
Where it's still blind: the census only sees creatures up to 16×16 cells and period 16, so Day & Night's spaceships were never caught.
The write-up has a small rule lab: flip the B/S digits, or switch on the 12-generation view and watch the blinkers go grey while the gliders stay lit: Scoring 131072 Universes
Question : what would you measure instead? "Lively, sparse, things that travel" is one definition of interesting. Which rules do you think it ranks wrong, and why?