Alex closed his book, finally understanding that the hardest puzzles are the ones most worth solving.

Suddenly, his grandfather, a retired engineer, sat down beside him. He didn't reach for a (answer key) or a "besplatno" (free) download online. Instead, he pulled out a handful of colorful buttons.

In the small, snow-dusted town of Logicville, a first-grader named Alex sat staring at a riddle that felt like a mountain. His workbook—the famous by Arginskaya, Benenson, Itina, and Kormishina —lay open to a page of complex patterns and curious number houses .

"You see, Alex," his grandfather whispered, "Arginskaya and her friends didn't write this to trick you. They wrote it to help you see the music in numbers."

"I'll never solve this," Alex sighed, his pencil trembling. "It’s like a secret code only the authors know."