I'm a bit disappointed that this thread didn't go anywhere, so allow me to rekindle it slightly. Here's a relatively easier puzzle they recently showcased which I had a go at myself prior to watching and found to be quite stunning.
An important thing to note is that a lot of handmade Sudoku puzzles like these will usually incorporate a vast amount of extra rule sets beyond the standard "digits 1-9 with no repeats in every row, column and 3x3 box". For example, this one is known as a Killer Sudoku, which adds "cages" of various sizes for digits to go into where they again cannot repeat, but must also sum to an associated number in the corner of the cage. As a starting point, this puzzle includes the "Odd/Even" rule where cells with a circle must contain an odd digit, and for further ease of solving, it also minimally includes the "Kropki dots" rule where digits separated by a white dot must be consecutive.
There are also the Even squared cells and black Kropki dot where digits on either side must be double/half or one another (2:1 ratio) but these are not included in this puzzle.
The brilliant thing about this one compared to usual Killers is that the cages are made to be seen as the nets of standard 6-sided dice, and so the numbers on opposite "faces" of that die must add to 7. It's the same gimmick that an entire little-known puzzle game I'm quite fond of,
Dynetzzle, was built around, so I was quite pleased to see that also incorporated in a Sudoku. I highly recommend this one just as much as CtC does in the video title; it makes for a very good primer on various pencil-marking and solving techniques such as naked sets and colouring, and is generally far better than your average randomly-generated newspaper Sudoku.
, and then people got hooked.
