Advent of code

I recently came a cross interesting December challenge.
It's called advent of code, it has quite interesting challenges that you can solve using any programming language..

Here some small info:

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.

https://adventofcode.com/

If you have some extra time in December feel free to participate.. :)