8:18 am
spellacked

a slow starter (should have been faster but I think I skipped a number on my first pass), but all falls in without greens.

2:16 pm
JudyHall

GREENS/AUTOGREENS comment: Whether one uses manual greens or the autogreens script, the initial objective in using greens is to fill in ALL POSSIBLE VALUES for an empty cell (and ultimately for each empty cell in the grid). Then perhaps a better perspective on the next steps in the use of greens/autogreens is to realize that, after entering greens, the puzzle solver's objective becomes the ELIMINATION of FALSE GREENS in order to find the correct value for a cell. To be honest, this approach to solving Sudoku puzzles has been fascinating to me, especially reading drwho's fantastic page on how to analyze greens to eliminate values that can't be correct. So, to me, it isn't that the greens autoscript puts in the correct value for a cell, but that the puzzle solver has learned to identify patterns that will ELIMINATE the INCORRECT green values. Would appreciate comments from @tuco and @drwho (from whom I have learned to very much!)

7:26 pm
TallMike

JudyHall, there is only one possible value for each cell because a Sudoku puzzle has only one solution. Technically, the autogreens script therefore displays the only possible value for each empty cell (the correct value) plus an assortment of impossible values (false greens).

Rather than writing, "the initial objective in using greens is to fill in ALL POSSIBLE VALUES for an empty cell..." you might more accurately say something like, "the initial objective in using greens is to display all the apparently possible values for each cell based solely on the absence of such numbers from the row, column and block in which the cell is located." It then becomes clear that false greens are subsequently eliminated by the player considering other criteria not included in the autogreens script.

This post is not intended as a substitute for the comments from tuco and drwho which you have requested and will no doubt receive in due course.

10:54 pm
JudyHall

Thanks, TallMike; your clarification is well stated.