This video might just be, for better or for worse, the most enthralling 25 minutes of your year.
It shows 46-year-old Simon Anthony, co-founder of the Cracking the Cryptic YouTube channel, tackling a seemingly-impossible Sudoku puzzle with added chess-related rules.
Anthony's videos have amassed 150,000 subscribers, and have provided some reassurance in these troubling times.
If you're thinking that it sounds like the nerdiest video you can imagine, you're entirely correct. And it's absolutely absorbing, with stunted silences ended by bewildered interjections ranging from 'you're joking' to 'you have got to be kidding me.'
(If the start is a bit slow, you can skip the first five minutes and head straight into the action.)