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That eater design is extensible: Not completely unlike the queen bee shuttle.

I found a potential shuttle in HighLife, but no stabilization: x = 3, y = 3, rule = B36/S23 3o$obo$bo! It creates a t-tetromino 5 cells behind it, and moves 3 cells in the other direction while flipping around in 12 generations. If there is a way to eat a HighLife t-tetromino in less generations tha...

Naturally occuring (!) quadratic growth: x = 306, y = 236, rule = 2356/3456/6 194.2A37.2A11.2A2.2A27.2A$3A15.A227.2A2.2A$ABA14.3A13.2A8.2A8.2A8.2A 8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A$EAE14.CBCA8.E3.2A8. 2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A8.2A$ACA14.ACD 2A$ABA14.B2.ABA...

c5/12 in B3578/S2356/n4: (VERY common): x = 11, y = 5, rule = 2356/3578/4 7.ABA$.2A3.CA2BA$3A.C4.2A$.2A3.CA2BA$7.ABA! A barge can reflect the 5c/12 90 degrees (once): x = 12, y = 9, rule = 2356/3578/4 .A$A.A$.A.A3.ABA$2.A3.BCACB$5.2ACBCA$5.2A2.3A$5.2ACBCA$6.BCACB$7.ABA! 3c/14 in B3456/S2356/n6: x = ...

B3/S1258 is very chaotic and Life-like.
B3578/S24678 or Geology is a very well-balanced and chaotic rule that forms large "continents" at a roughly 50% density, but they eventually erode away into smaller "islands".

How about B3/S1256? I was looking for chaotic rules with S1 (I decided on its neighbor B3/S126) and I found this VERY slowly exploding rule. Though there are plenty of patterns that settle down. EDIT: 124567/345678/18 (a.k.a. the result of me trying to cram as many Bs and Ses into a Generations rule...

A slew of very high-period oscillators in B36/S258 occur from 92+-cell lines. Oscar couldn't find the 92 after 10,000,000 generations

Josh Ball's B26/S08 c/5 spaceship: x = 18, y = 56, rule = B26/S08 7bo2bo$3bo4b2o4bo$6bob2obo$6b2o2b2o$7bo2bo$8b2o$2bobobob2obobob o$bo5bo2bo5bo2$7bo2bo$7bo2bo$6bo4bo2$7b4o$5bo6bo$5bo6bo$5bo6bo$4b o2bo2bo2bo$8b2o2$8b2o$7bo2bo$3b3o6b3o$8b2o$4bo8bo$7bo2bo2$8b2o2$ 2bo2bob4obo2bo$3b2obo4bob2o$3bo10bo$7b4...

Actually, wouldn't the spaceship with the double diamond spark be a geminoid? A domino evolves into 2 of these, facing opposite directions; and a domino features as the front (in the leftmost spaceship) and creates another in the same direction, while the back duoplets "eat" the one going the opposi...

B26/S08 is an exploding rule; however, I have found quite a few oscillators and spaceships, as well as a puffer. This rule is similar to Live Free or Die, but the B6 changes behavior on the more complex scale, and S8 on the more simple scale. For example, a 3x3 box in B26/S0 is a spark, but in B26/S...