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Online comment platforms can bring out the best — and the worst — in people. At the end of a tumultuous year, *Quanta*’s editors highlight some of our favorite things you had to say.

While the study of the SARS-CoV-2 virus was the most urgent priority, biologists also learned more about how brains process information, how to define individuality and why sleep deprivation kills.

Even as mathematicians and computer scientists proved big results in computational complexity, number theory and geometry, computers proved themselves increasingly indispensable in mathematics.

Featuring paradoxical black holes, room-temperature superconductors and a new escape from the prison of time.

Physicists saw a black hole for the first time, debated the expansion rate of the universe, pondered the origin of time and modeled the end of clouds.

Researchers explored the zone between life and death, charted the mind’s system for arranging ideas and memories and learned how life’s complexity emerged.

Mathematicians and computer scientists made big progress in number theory, graph theory, machine learning and quantum computing, even as they reexamined our fundamental understanding of mathematics and neural networks.

Celebrate a year’s worth of scientific and mathematical insights by solving this brain-teasing cryptic crossword from our puzzle columnist.

Several mathematicians under the age of 30 left their marks all over the field, and amateur problem-solvers of all ages made significant contributions to long-dormant puzzles.

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