drc wrote:superstrijder15 wrote:Im [p]retty new to CGOL, but for question 2. I'd like to know if there is any finite sized pattern which can stop an infinite amount of each concievable spaceship from any direction(a kind of ultimate eater)! And if there isn't, is there a finite pattern which can stop one or multiple spaceships from any direction...

That's most likely impossible...

To be a little more specific: people have spent quite a bit of time trying to come up with the most likely defense mechanism for something like a quadratic replicator.

The theoretical question is something like this: in a Life universe with very sparse initial conditions -- most cells OFF, but each cell with a tiny chance of being ON -- all sorts of different patterns will spontaneously come into existence very very very far apart from each other. Here and there on an infinite Life grid you'll even see spontaneous replicators. Would there be a replicator with a good enough defense mechanism, that it would eventually outcompete all other replicators and take over the whole Life plane... after a very very very very long time?

Simple Stuff Works BetterSo far it seems as if a simple passive defense is the only thing that would be moderately useful. For example, if I haven't made a mistake in setting this up, three rows of carefully spaced blocks can successfully absorb a glider on any lane from any direction, with no possibility of starting a chain reaction.

`x = 746, y = 746, rule = LifeHistory`

72.2A$72.2A35$72.2A46.2A$72.2A46.2A35$72.2A46.2A46.2A34.2A34.2A34.2A

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34.2A34.2A34.2A34.2A34.2A35$72.2A46.2A46.2A$72.2A46.2A46.2A11$204.2A

34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.

2A$204.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A

34.2A34.2A23$72.2A46.2A46.2A$72.2A46.2A46.2A23$204.2A34.2A34.2A34.2A

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46.2A$72.2A46.2A46.2A23$576.2A46.2A46.2A$576.2A46.2A46.2A11$72.2A46.

2A46.2A$72.2A46.2A46.2A23$576.2A46.2A46.2A$576.2A46.2A46.2A11$72.2A

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11$72.2A46.2A46.2A$72.2A46.2A46.2A23$576.2A46.2A46.2A$576.2A46.2A46.

2A11$72.2A46.2A46.2A$72.2A46.2A46.2A23$576.2A46.2A46.2A$576.2A46.2A

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576.2A46.2A46.2A11$72.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A

34.2A34.2A34.2A34.2A$72.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.

2A34.2A34.2A34.2A34.2A23$576.2A46.2A46.2A$576.2A46.2A46.2A23$36.2A34.

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2A$2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.2A34.

2A34.2A34.2A34.2A46.2A46.2A35$624.2A46.2A$624.2A46.2A35$672.2A$672.2A

!

So there's a safe area in the middle of the above square... until a second glider comes along. Even having six rows of blocks (or more) instead of three won't necessarily provide safety from a second glider impact -- the second glider might hit an ongoing pi explosion from the first impact and set off a large uncontrollable reaction. A quick automated search could pick out the most explosive combinations.

Also of course this particular setup will stop a single glider, but it's terrible at guarding against orthogonal spaceships. You could fix that, but there would be other vulnerabilities. Each type of spaceship allows for new chain-reaction threats, and there are an infinite number of different spaceships. For any given defense wall, an automated search utility (with a large spaceship library) could take as long as it needed to find the exact attack point that would do the most damage.

What If It's Not Passive?It's tempting to consider an active defense -- maybe a similar wall of blocks, but one that is monitored from inside the wall and repaired when it gets damaged. But it turns out that any possible repair mechanism is probably more vulnerable to attack than the simple static wall would be. Let's say the monitoring reaction takes N ticks to reach out, make sure a block is in the right place, and fade away. Our theoretical search utility now has N times as many possible targets to try hitting with spaceships, making it (most likely) about N times more likely to find a devastating weakness.

Possibly the perimeter could be patrolled by very cleverly designed salvos of gliders, where each salvo is designed to fade away cleanly if it hits Spaceship X, and fade away cleanly using a different mechanism if it hits Spaceship Y, and so on. But again, the bigger and cleverer the salvo is, the more different ways there are to hit it with something that the salvo designers didn't guard against...!