Logic Masters Deutschland e.V.

Rules

• Normal Sudoku rules apply: Place the digits 1-9, once each, into every row, column, and 3x3 box.


• Nurikabe: Shade some cells blue (representing water), such that all water is orthogonally connected, but does not fully cover any 2x2 area. Non-water cells form groups, representing islands (shade the islands in your favorite blue-contrasting color).


• Skyscraper (non-standard): Clues outside the grid indicate the number of islands (not island cells) seen in the indicated direction.


• The height of an island is equal to its largest value. Taller islands block vision to shorter islands (or islands of equal height). Digits on islands may repeat, if allowed by other rules.


• Fortress: Wherever an island cell borders a water cell, the digit in the island cell is larger.


• Kropki: Digits separated by a black dot have a 1:2 ratio. Digits separated by a white dot are consecutive.


• Additionally, black and white dots may not lie on a border between island and water.

Further clarifications, for the avoidance of doubt

• There are no negative constraints of any kind (absence of a black/white dot or skyscraper clue are meaningless)


• There are no restrictions on island sizes or the digits that must appear in islands, beyond what is required by the rules above (i.e. islands need not be of different sizes, islands need not contain the digits from 1-N)


• The height of the ENTIRE island is equal to the largest digit, regardless of which cells are seen by skyscraper clues. For example, suppose an island (spanning multiple rows/boxes) contains the digits 5-6-6-8. If a skyscraper clue only sees the "5" (because the other digits are perhaps in other rows), the height of the island should be interpreted as "8".



Puzzle Link

• SudokuPad


Background

This puzzle is named after Princess Elsa’s song in “Frozen”, which also inspired the ruleset.

I want to express my gratitude once again to Christounet and Niverio for their testing and honest feedback on the first version of this puzzle. Their comments inspired me to keep refining my ideas and smooth out the solve path with a more elegant ruleset, resulting in a final version that I love.

Even after the improvements, I hesitated to publish it, concerned that the fortress constraint may not resonate with many solvers. Ultimately however, I decided to embrace the spirit of the puzzle’s namesake and “Let It Go”, setting aside my worries about how it might be received.

Finally, I also considered writing the ruleset in terms of “ice castles” instead of “skyscrapers”, “fjords” instead of “water” and “snowballs” instead of “white kropki dots”. However, I concluded it was best to adhere to convention, at least in the official version. Solvers are encouraged to visualize the constraints in this manner, if desired!

If you ever need a logic check, hint, or nudge, please reach out to me on discord at MaizeGator