This was my tenth(!) year building 25 days of puzzles for #AdventOfCode. You can solve them all for free! Most people write code to solve them, but you can solve them however you like. I hope they help people become better programmers. 🌟

The first puzzle comes out in two hours: https://adventofcode.com/

Advent of Code 2025

@ericwastl I never participated, but I know people that have. Has there ever been a chemistry themed one? Is that still available?
@egonw There have been a few chemistry-themed puzzles, I think; all puzzles are still available.