Advent Calendar of Math Games

First, found NRICH, a very cool website with "thousands of free mathematics enrichment materials (problems, articles and games) for teachers and learners from ages 5 to 19 years."

Second, noticed that it contains an Advent Calendar with a "mathematical game for each day during the build-up to Christmas." You just click on the date to see a new game. Most of them are on-line, interactive. Fun stuff!