I did this Advent Calendar for BESTSELLER's stores as a fun way for their employees to learn about their new cash register system. The idea was that every day there would be a new tool tip for how to use their cash register. The tips was a top up to the shop assistant's foundational knowledge about the cash register system. 

However, do to the costs of producing the Advent Calendar, it ended up being a poster. The shop assistants could then go to their intranet and find new tips every day.