Three more Basic victories are reported here with interesting traces. Looking ahead, the blog is heading toward more advanced collections, with this series being the final statement on Sysudoku Basic.
Ppbr 57 starts remarkably like ppbr49. C1 makes a wall for the value 1, forcing NE1. S1 is not first, only because of the convention to scan floors North to South and boxes West to East.
The bypass trace is stretched across the page by 3-fills.
Master Class 70 offers another unusual Basic start, in which values 1 and 5 are detected working together to claim two cells of NW. Then 4 and 8 claim two cells in SW to place SW7.
In box marking, 70 soon gives up a rare gem. Look at NE at 6: NE. The four valus 2,3,4 and 6 are confined to four cells. It’s a naked quad. No other candidates can be added to these four cells, so NE4 is confirmed immediately.
Naked subsets can be found in box marking before all candidates are known. Hidden subsets require that all candidates of the unit be known.
Here is the basic trace, showing the follow up to NE4. Collapse comes in line marking. In the earlier review, Master Class 70 made it into advanced, for a Sue de Coq, XY ANL, or a swordfish.
Tom Sheldon’s 80 was a highlight in the February 2013 review. Here is the grid with highlighted naked triple, as it appears in the update, in early line marking.
As evidence of an improved Sysudoku Basic, compare the trace of 2013 with this one.
Take into account that the difficult line marking of 2013 is not completed.
Including Master Class 80 here, the next stop of the bypass express is at PencilPress Extreme br 73 at left and Master Class 90.
Both are basic level, but barely.