The adults are wiped out by a cosmic event that results in the Lord of the Flies on a planetary scale. Liu uses some hand-wavy logic to explain how only the adults were affected by the supernova, which is rather uncharacteristic of his writing. Normally he goes into dissertation-level detail behind the science of major events. Scientific realism is his brand, so it it was a surprise to see that lacking. The story does have some interesting plot points and a few unexpected turns, but overall it's rather boring. Out of all the Liu's stories that I've read, this one is mostly written from a larger macro perspective, which gives it a sterile and detached feel. There's very little character development or backstory. Liu goes into great detail describing the child war games, but I ended up skimming most of that because I didn't care. Overall, this is my least favorite Liu book/story. Maybe the premise would've severed better as a short story or novella instead of a 350 page book?