- Technology Marches On: Justified, given that the books were written in 1997.
- A kid living next door to Pyotr asks him to play a new game over the Internet. Pyotr agrees, as long as his grandfather allows him to hog the phone for a few hours. These days, dial-up connections are largely on their way out in most of the developed world (yes, that includes Russian cities).
- While on the Geometer homeworld, Pyotr (still thinking himself to be Nik) is introduced to the local "books", which are described in terms not unlike modern e-readers, with the main difference being that e-readers can be loaded with hundreds of books, while each Geometer "book" is just one.
Trivia / The Stars Are Cold Toys