Configurations considered: first-crossing, blue-loop, and mixed
There lived a little star named Luna. She was a special kind of star called a Cepheid, which means she would sometimes shrink in size and sometimes grow back bigger again. It's like when you blow up a balloon to make it big, but then let the air out and it shrinks again!
Technical definition
In this context, "configurations" refers to different theoretical models describing the state of a Cepheid system (e.g., whether it has undergone a first-crossing (expansion), moved through a blue-loop stage, or exhibits mixed behavior).