Advent of Code is an Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like. People use them as a speed contest, interview prep, company training, university coursework, practice problems, or to challenge each other.
If you'd like to support Advent of Code, you can do so indirectly by helping to Share it (via Twitter or Reddit) with others, or directly via PayPal or Coinbase.