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
Note: Follow this link for other less common number placement variations.