An interesting result in the current issue of Earth and Planetary Science Letters, suggesting that Earth may have had a significant ring system lasting up to 40 million years during the Ordovician period, about 466 million years ago:

https://www.sciencedirect.com/science/article/pii/S0012821X24004230

The mechanism is particularly interesting, and has implications for Architect of Worlds. At present, the design sequence simply will not produce rings around a terrestrial planet comparable to Earth. In this case, the hypothesis is that a largish asteroidal body had a near-miss encounter with Earth, within the planet’s Roche limit, and broke up to form rings. Which suggests that any terrestrial planet in a system that includes at least one planetoid belt might have a temporary ring system at any given time.

I’ll have to think about this some more, but there might be some additional guidelines forthcoming to cover this case. Not to mention that a ring system would cut back on insolation and have a profound effect on planetary climate . . .