## Puzzle 213 (Nurikabe) [No 5-lines]

This is a Saturday Nurikabe puzzle, with a twist. The rule that there may be no two by two square of black cells is lifted. In its place is the rule that you may not have five consecutive black cells in a row or column. (Equivalently, the original rule stated that you could not overlay a square tetromino on the black cells, and the new rule states that you cannot overlay an I pentomino on the black cells.)

Puzzle 213

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### 8 Responses to “Puzzle 213 (Nurikabe) [No 5-lines]”

1. Alan Curry Says:

I was skeptical about the 5-bar rule being a worthy substitute for the pool rule, but it turned out to be just as good, maybe even better. When you remove a cell from a 2×2 square, it doesn’t matter which one you pick, you just get rotations of the same shape. With the 5-bar, there are 3 different configurations.

2. Jack Bross Says:

This was a nice balance between preserving the solvers existing experience and strategy for nurikabe, and forcing them to think about the new twist. Solving it led to a nice feeling of continual discovery as I figured out ways in which the 5-bar rule could come into play. I always enjoy when a nurikabe sets up a tempting (but false) option and then thwarts it — a sort of logical pun. In this case, early on in the bottom right, the moment where I knew this was going to be fun was “hmm, this row of three white squares could just continue on and connect to the 5, or I guess it could dogleg up to the 6, so …. oh …. no 5-bars means … OH!”

3. MellowMelon Says:

As Jack noticed, there’s more to the 5-bar rule than just the feature Alan Curry mentioned about there being multiple configurations. Some white cell configurations are completely forbidden.

I will admit that from a construction standpoint Nikoli’s rules for this puzzle are probably better. It can be tricky to try to work neat solving elements into a puzzle with these rules, and sometimes I had to struggle to deal with some stray white cells the rule created. But I think the solving potential is at least as great if the required amount of construction effort is put in.

Thanks to both of you for the comments.

4. yy Says:

Very nice. The solution flowed nicely once I got used to the new rules.

5. TheSubro Says:

Nice variation. Probably harder for you to construct than for us to solve, but it certainly had many pause and pause and consider moments. It also taught me to focus more on how certain cells will closing off exit/connection routes. It is not a new idea but less emphasized in most standard Nurikabes – where the focus seems to be more of “how do a get an “island” to reach to this point so as to avoid a 2×2 constraint.”

Well done. Thanks.

Ken

6. mathgrant Says:

You sick, twisted man. Do you know how much sheer willpower it took to not make deductions based on certain old Nurikabe habits?

Well, actually, it wasn’t that hard. But still! Nicely done, by the way.

7. zyzzyva Says:

This comment might be a little late, but this is a really interesting constraint, and it would be interesting to apply it to other puzzles. The first puzzle that came to mind was LITS, with this new constraint all five tetrominoes would be allowed. (LOITS?)

• MellowMelon Says:

I think I like TOILS better as an acronym. 😛 On the topic of other “no 2 by 2 island” puzzles, there’s also the much less common Mochikoro. That one deals with rectangles, so the new constraint would have a huge impact there too.

I might have to explore the TOILS idea some; I have trouble expressing myself in LITS, but maybe I can do something creative with the variation.