Cave by Thomas Snyder

[This is a repost from our archives with new notes at the top (original post here): One of my favorite “underappreciated” puzzle styles is Cave, a genre that began as BAG from Nikoli (with rules consistent with other loop puzzle styles). The style passed through other names like Corral in the United States Puzzle Championship before being recast as a shading puzzle as Cave which is the GMPuzzles name. While the shading approach feels most natural to me, it does have one slight disadvantage from the loop version which is solvers need to learn an anti-checkerboard rule for themselves (i.e., you cannot have a 2×2 square which alternates between inside/outside cells as on a checkerboard). In the “loop” version of the rules, that grid state would require drawing four edges through a point and would violate the non-intersecting loop rule.

However you want to refer to this puzzle style, we hope that you enjoy this look back at some of the first Cave puzzles on the GMPuzzles site starting with this one featuring a long diagonal of clues.]

Cave by Thomas Snyder


or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s)

Theme: Ascending/Descending Diagonal

Rules: Standard Cave rules.

Estimated Difficulty*: 1.5 stars

Time Standards (highlight to view): Grandmaster = 0:45, Master = 1:20, Expert = 2:40

Solution: PDF

Note: Follow this link for classic Caves and this link for Cave variations. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on. More Cave puzzles can be found in Roger Barkan’s Colossal Cave Collection, in The Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

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