Tungsten Red is an illustrative example of the general pattern that it shares with the other Sudokus in what we might call the “Precious Metals” series-Platinum Blonde, Golden Nugget, Silver Plate, and Bronze Medallion (videos 14, 15, 44, and 45)-and several other Sudokus for which there are videos on this channel: Red Dwarf, Discrepancy, Fata Morgana, First Peak, Trompe l’oeil, coly013, and tarx0134 (videos 16, 24, 29, 32, 30, 17, and 18). This pattern emerged some years back when a group of theorists and designers were working together to create the most difficult Sudokus possible. It was challenging to computer algorithms then, and it remains challenging for many algorithms even now.
I take a different approach from those algorithms. They typically fill in all possible candidates in unsolved cells and then seek to eliminate all but one number in each cell. Instead, I supply two or three numbers whose placement the overall design of a puzzle suggests would be reasonable and promising. In this case, I added the numbers shown in this video at 00:13 and 00:55. The result was a solution that played out in classic form: increasing complexity even as cells steadily filled in, sometimes through involved tactics (such as in the sequence beginning at 01:57); an impasse that a simple forcing chain broke through (starting at 02:36); and an orderly resolution from there. I feel that Tungsten Red illustrates clearly the combination of strategic and tactical considerations that I have been discussing in regard to these puzzles. I think it also shows how a solution to them can be not just correct but also aesthetically satisfying.