Broken Sign Blog
#163: Rail Pool (Even/Odd)
30 March 2025This is the other puzzle that won Logic Showcase 67. For this one I wanted to take the “logic showcase” idea a bit more literally and make a big puzzle to show a wide variety of deductions, without going too crazy on interpreting the prompt.
Applying the Even/Odd variant to Rail Pool was originally Prasanna’s idea, but I also made one of these before. The large grid also let me work with very large segment lengths, which is something I’m often hesitant to do in my Rail Pools. Originally, the puzzle was going to be 20x20, but I saw some nice logic I could get by shrinking the grid a little.
Rules: Draw a non-intersecting loop through the centres of all cells. Some boldly outlined regions contain number clues. If a straight loop segment visits any cells of a clued region, its length must match one of these numbers. Each number must correspond to at least one such loop segment. Question marks represent any positive integer, but numbers cannot repeat within a region.
Variant: Even/Odd — Each “E” represents an even integer, each “O” represents an odd integer. As with question marks, numbers cannot repeat within a region.