Some problems of the popular Christmas "office-entertainment", "Secret Santa" game, are discussed in this Numberphile video.

Have you ever considered a simple question - what do the numbers you see in your banking account mean? Have you ever questioned yourself why some plastic card is accepted at stores? Everything seems simple - people just believe in money and furthermore electronic transactions. But humanity has walked a long way until we have reached modern understanding of money. Actually it took quite a long time to accept money as they are accepted now. We invite you to watch an excellent tale by Extra Credits on the history of paper money. Below you should see a link to their first video on this topic.

In the first half of the 18th century citizens of Königsberg were very proud of their city and the seven bridges located in it. It is said that city had great views near the river, so the citizens liked to take walks by the river. While on a walk they, obviously, had to traverse the bridges. Naturally the question emerged - would it be possible to choose path so that it would allow to traverse each bridge only once. The answer and the analysis of the problem maybe found in this video by Numberphile.

Evil syndicate has built a 10 floor pyramid. This pyramid has a lot of empty rooms, while there is one control room, which hosts control machine for the super weapon, which you must destroy. The problem is that you do not exactly know on which floor the control room is. You only have a couple cryptic clues...

Mike Rugnetta and the team behind the PBS Idea Channel each week tackle an interesting idea or question related to the contemporary life. We share their video in which they tackle a question intimately related to the themes covered in Physics of Risk blog - how to control social systems (see related post).