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Monday Mutant 22: Battleships (Shinro)

Ten ships (as indicated below the grid: one four-cell ship, two three-cell ships, three two-cell ships, and four one-cell ships) are hidden in the grid. The ships may be rotated from the orientations shown, but may not overlap or occupy cells which share a corner or an edge. A number to the right of a row or below a column indicates how many cells in that row or column are occupied by ships. No cell containing an arrow may contain part of a ship, but every arrow must point to at least one ship segment in that row, column, or diagonal (although not every ship segment needs to have an arrow pointing to it). Locate the ships.
This variant is inspired by a puzzle called Shinro, a puzzle apparently of Japanese origins.


ralphmerridew said...

Is Shinro the original name for Stargazers?

Jonah said...

Nice one.

There was a really interesting step in the middle. It's common in that stage of a Battleship puzzle to eliminate a move because it would require more than k ships of size 5-k, but in this case the contradictory move would have required 11 ships total (whose sizes I didn't know)! I don't think I've seen that before, at least so early in a puzzle.

Grant Fikes said...

ralphmerridew: I have seen Stargazers before (and, in fact, posted a comment on Zotmeister's aforementioned Stargazers puzzle four years ago), but I've only known about Shinro for a few days now, having first been introduced to it by the iPhone app Jabeh. Prior to that, all of the Stargazers puzzles I've seen have a rule that all stars must have an arrow pointing at them; the ones on and Zotmeister's blog are even more specific, stating that every arrow must point to exactly one star, and every star must have exactly one arrow pointing to it.

Honestly, I have no idea whether Shinro or Stargazers came first. According to, the origins of the Stargazers puzzle genre (known as Sternenhimmel there) is unknown. The page makes no mention of Shinro, though. Maybe Shinro's based on Stargazers.

Grant Fikes said...

Jonah: While that logical deduction could conceivably have been made in the middle of the puzzle, as you did, when Joseph DeVincentis solved it, that step was his last step. I had the step planned from the start, though -- it was a matter of figuring out how to construct the puzzle to force it. :) Thanks!

Jonah said...

Just looked up Jabeh. Huh. Would you recommend the download?

Grant Fikes said...

I haven't tried the full version; I've only downloaded the free lite version. The music is very beautiful and, in combination with the visuals, lends a pleasant, non-distracting atmosphere to the game. My biggest problem, though, is that it doesn't let you pick individual puzzles, though. From the Lite version's description, I gather that the app comes preloaded with puzzles (7 for the Lite version, and 150+ for the full version which costs $4.99) and chooses a random puzzle of your preferred difficulty (Easy, Medium, Hard, or Any difficulty), rather than generating puzzles on the fly. While the latest version of the full app ensures that you won't see repeated puzzles until you've solved every puzzle of the chosen difficulty, I want to be able to choose a specific puzzle if someone tells me, "Hey, this specific puzzle is awesome!"

*shrugs* I can't make a recommendation for or against this title, really.

Anonymous said...

NICE ! Very enjoyable solve.


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