Thanks!
When I first came up with the idea I also thought that it would have appeared somewhere else by then, since it seemed so simple, but apparently not so.
The reason I made even numbers unstable was simple: even numbers split in half nicely, whereas odd numbers don't, so even numbers could split evenly between 2 neighbouring circles but not odd numbers.
I was actually quite surprised some people were confused about the mechanic, since I thought the tutorial was quite good at explaining that, at least to me. Guess I will need to rework it a bit.
But overall, thanks again for the positive feedback!