Blueprints of Mt. Holly
(Published on 30. January 2026, 21:38 by alhobj)
Make your way through the mansion at Mt. Holly. Inspired by Blue Prince (no spoilers).
Each room has nine cells that contains digits with a meaning shown in the picture below.
- Cell 1: The sudoku digit of the room (1-9), cannot repeat as a sudoku digit in other rooms in the same row or column.
- Cell 2, 4, 6 and 8: A 1 indicates a door in that direction, a 0 indicates a wall. If a room has a door the room next to it has to have a door facing it. The same is true for walls.
- Cell 5: The room type shown in color and matching number (1-6)
- Cell 3: The number of doors in the room (1-4)
- Cell 7: Sudoku value (-9 - 18)
- Cell 9: Door value (-4 - 8)
The parity of the door digit in a room equals the parity of the sudoku digit in the same room.
Each room type modifies the sudoku digit (cell 1) to give the sudoku value (cell 7), and the number of doors (cell 3) to give the door value (cell 9) in the following way:
- Blue room (Value = Digit)
- Red room (Value = - Digit)
- Green room (Value = 2 x Digit)
- Orange room (Value = 0)
- Gold room (Value = 1)
- Purple room (Value = 2 + Digit)
Note that both the sudoku and door value can be negative, I suggest marking the negatives in red. The sudoku values can be two digit numbers, write the last digit and mark it in green (14 becomes a green 4)
For each row the sum of the values equals the rank of the house shown on the left. The same is true for the door values.
A correct example of a 3x3 house is shown with paths marked for clarity. Note how the sums of the sudoku values equals the rank (example 0 + 0 + 1 = 1). And that the same is true for the door values (example 0 + 5 - 2 = 3).
Start in the entrance hall in the middle of rank 1. You can assume all outside walls are walls and do not have doors.
Sudokupad link: https://sudokupad.app/f4yexs1adz
Solution code: The sudoku digits in rank 1 left to right (5 digits)
Comments
on 8. February 2026, 21:21 by CitrusGremlin
what a lovely homage! Was intimidating at first but rapidly started to fall apart once I got going.
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Thank you!
on 4. February 2026, 20:36 by webato
very cool!
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Thank you!
on 31. January 2026, 18:27 by firespire
The rules take a bit of study and then I still messed up which cells are the same odd/even. Thank goodness for solution checker. It's a long quest but not tricky after understanding how to follow the rules.
In cleared empty cells the outside wall isn't a door but you can't make that assumption to anything under the fog.
Mathematics isn't my strong point and I may have spent too long assuming it was always solvable early on when I should have left it until I absolutely run out of other things to do and then it was easy.
I don't know much about Blue Prince and despite being told a starting position, building a valid path was never used in my solve, the solve just involved working out the digits from the rules.
Best on a bigger screen, I used a small screen device but it has accessibility settings and a zoom window option for visually impaired people that I could turn on and off but it was tricky to use.
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Thank you for the long comment that clears some things up :)
Small screens are definitely not recommended for this one.
on 31. January 2026, 13:01 by davidemsa
The Blue Prince theming of this puzzle is amazing. There are a lot of rules to learn, but it's worth it because they makes us think of different things than usual.
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Thank you!
on 31. January 2026, 10:45 by alhobj
Changed the example house, so it follows the parity rule
on 31. January 2026, 02:45 by Titan29
Love Blue Prince! I agree with HerrEks that the garage reference was so fun but I also agree with godoffours that it's a bit confusing considering it breaks the rules of the puzzle.
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Thank you for the comment! As I wrote in the hidden comment, I thought the sentence "You can assume all outside …" would let me have an outside door if it was given and not found by the solver. It might be because English is not my mother’s tongue, but I cannot think of another way to write it to keep the surprise and make it clear that it is allowed.
on 31. January 2026, 00:05 by HerrEks
Awesome puzzle! Rules seem overcomplicated but are actually pretty smooth once you get the hang of it!
Although it took some time to understand the ruleset at first because the example doesn't follow the parity rule.
PS: The reference to the garage made my day!
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Thank you so much!
I did not realize that the example house did not follow the parity rule. I will ponder and see if I can think up a new example ;)
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After some ruminating, I found a new example house that works! Thank you for letting me know
