I have really enjoyed doing this in previous years. There is a leaderboard for who can solve each day the fastest, but I just ignore that and enjoy the puzzles. It gets a bit tricky to fit in when the puzzles get longer, I have a day job and the children finish school for Christmas but it's worth getting up early for. Many people seem to use this as an opportunity to learn a new language.
https://news.ycombinator.com/item?id=29292818 (731 points/196 comments)