PencilPress  500+ Sudoku Extreme Puzzles rates in Sysudoku as basic level, with most of the preselected puzzle on the bottom right corner of pages 9, 16, . . ., being solved in the bypass. In each of the posts verifying this, an advanced topic is also included. This time it’s an alternative solution, without trial, of Rebecca Bean Extremely Hard, section VI, # 24.

Any trace of a solution in the bypass is going to look complicated, but the most moves are simple. Then, as you read the trace by filling the grid, some moves are not. The value of reading a trace is that the reason for the move forms in your own head. Always formulate the reason there before you update the grid. It’s profitable to think also of why the current move was spotted. What change in the grid prompted it?  Sysudoku basic traces follow a protocol. You don’t have to know what it is, but after reading a few traces, you’ll know it anyway.

Here is a bypass trace for bottom right 9:

It starts with the short 5-chain ANL found before coloring. But that blinded me to the 2-chain ANL running alongside.

The elimination sets up two slinks for a grouped skyscraper ANL.

The coloring trial is still available, but Sudokuwiki goes for AIC building, and finds

this confirming ANL.  You or I might be on a boomerang search, but  arrive at a slink into the starting 8 instead of a wink into  2 or 5. That’s a bonus for looking.

The new clue S8 is decisive:

For next time, you can bypass your way through PencilPress bottom right, page 17,

then see if you need to read my trace.

Advanced readers get another go at III-47 from Moito’s Road to Mastery, which was finished with a coloring trial in the post of 1/02/18.