Easy as ABC (Transparent) by Prasanna Seshadri
or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a letter entry mode and a shading mode. CAPS LOCK is recommended for letter entry.)
Theme: Clue Symmetry and Logic (originally on 2016 Polish Puzzle Championship)
Author/Opus: This is the 120th puzzle from our contributing puzzlemaster Prasanna Seshadri.
Rules: Fill some empty cells with the letters A-F (A-D in the example) so that each row and column contains each letter exactly once. The letters outside the grid indicate the first letter seen from that direction, but each row and column has one transparent letter that is ignored by the clues. The transparent letters must be different in each row and column.
See also this example:
Answer String: Enter the letters (including the transparent letter) in the marked rows in order from left to right, separating each row’s entry with a comma. USE CAPITAL LETTERS.
Time Standards (highlight to view): Grandmaster = 2:45, Master = 5:00, Expert = 10:00
Solution: PDF
Note: Follow this link for other less common number placement variations.
10:30
I believe this puzzle is ambiguous. Is there a rule missing? In the example all the transparent squares are different, is that meant to be a rule? My co-worker and I both got different completely valid grids that are claimed to be incorrect on here.
The last rule (the transparent letters must be different in each row and column) needs to be applied. Another way to say this is the transparent letter set must be A – F without repeats. Apologies if the wording was confusing.
Ahhh. That clarifies things considerably. I had reached a dead end, but I think I’ll actually be able to solve this one now. 🙂