I finally played around with the latest binary for a while.
The main problem i noticed was that "Growth" no longer has a target. If i'm reading it correctly, when you set a planet to "growth" you get of the current capacity 100% instantly. There's no ramping up and ramping down like the other resources have. If somebody captures your breadbasket, you can instantly start up another elsewhere just as good (minus whatever growth buildings)
Yeah. The rationale for that was that I wanted Growth to represent exactly the amount of extra population the planet is providing for other planets. This shouldn't be too high, ever, (I believe no more than 8 as things are now, which seems pretty reasonable - it was 20 when species bonuses were applied last), and for a species with no Growth bonuses, no more than 5. The disadvantage from switching between different Growth planets would be nothing more than a minor nuisance, rather than a real drawback, so I just made the meter unpaired. I think it would probably be good if most or all growth bonuses came from buildings rather than from techs directly, so without buildings, the best you could get would be growth of 1, plus species bonus.
I'm not sure what the reason for subdividing growth into 20 levels is. Hopefully it's just a temporary technical neccesity.
It is a technical necessity, but not necessarily a temporary one; the options are to either:
a) Have the Growth planet directly give bonuses to planets in range as before. This prevents any way of selecting the largest bonus.
b) Have the planets getting the bonus select a bonus from their own effectsgroups based on some attributes of planets in range (in this case, within the same resource group).
b doesn't really work without discretized levels of growth, because as far as I know, there's no way to increase target population proportional to the Growth meter of the Growth planet, because we don't have reference to it. We just know that it exists because the activation condition was met. The way to work around that is to have the numerous effectsgroups that exist now - this way we know to an accuracy of 1 what the best Growth planet in range is, and we can give ourselves an appropriate target population bonus.
We don't need all 20 anymore though. At most, we'll need as many as the magnitude of the greatest Growth population bonus we'll want to be able to give, times the number of species groups, if we want to do that (and not all species groups need have the same max growth bonus, either).
I had a colony relying on a growth planet. When i changed the foci, boom, the colony was gone. No starvation, no gradual decline.
That sounds like a problem with population decreasing towards target too rapidly, unless the colony was very very small, in which case it's what I would expect.
We have a small number of foci to use for a large number of planets. I don't think we should have the goal of making any of the main foci only useful a few times per empire. That hurts the focus diversity of the remain planets as there are fewer useful foci to go around.
I don't object in principle to Growth being a commonly used focus, but it seems that it requires the rules for its benefits to become more and more complicated for the player to keep track of and optimize.
The difference between Growth and the other foci is that the benefit to using the other foci is always clear - you get more of whatever that focus produces. Growth doesn't produce anything, but rather gives a conditional bonus to other planets in the same resource group, according to some special rules, which makes its use more complicated. In that sense, it shouldn't be compared to the resource foci.
That being said, I wouldn't mind giving it a try if you want.