Cambrian
(Published on 2. October 2025, 21:23 by Kafkapharnaum)
RULES
Normal sudoku rules apply: Place the digits 1 to 9 in each row, column, and 3x3 box.
STILL LIFE (after Conway's Game of Life)
Shade some cells green ("active cells") such that the – up to – eight cells neighboring each green cell contain exactly 2 or 3 other green cells and the neighbors of each 'unshaded' – or black/red/etc. – cell ("inactive cells") do not contain exactly 3 green cells.
– A CIRCLED cell's digit indicates the number of cells that are in the SAME state as its own in its neighborhood, including its own cell
– A SQUARED cell's digit indicates the number of cells that are in a DIFFERENT state from its own in its neighborhood (therefore not including its own cell)
RENBAN
– Each purple line must contain a set of non-repeating consecutive digits, but not necessarily in order.
– Every digit on a purple line must either be a valid CIRCLED cell or a valid SQUARED cell, or both at once, per the Still Life rules.
==== EXAMPLES ====
In Example 1, a 3x3 box with a Game of Life pattern is shown (green for active cells, grey for inactive cells). But the cells marked with a ! are unstable : they either are inactive but with 3 active neighbors, or active but with less than 2 or more than 3 active neighbors. Therefore this pattern is not a Still Life pattern, and can not appear in a Still Life Sudoku puzzle.
In Example 2, a 3x3 box is shown filled with digits and clues (circles and squares), the Game of Life pattern that is shown is stable, and all the clues are fulfilled. This could appear in a Still Life Sudoku puzzle. John Conway Game of Life
Solution code: The 'active' cells of row 2 (left to right), followed by those of column 7 (top to bottom)
Comments
on 14. October 2025, 22:59 by wullemuus
What a surprise, Still life is back! Interesting approach with these hidden squares and circles and the leading renbans. Really elegant to solve!
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Thank you so much for the kind words! Indeed, bit a of a setting spree in the middle of an extended break, but I'm happy to have done it and see you having fun with the puzzle, and yep, the Still Life ruleset! And you get not just one, not even just two, but *three* for the price of one, as this one immediately gave me an idea for an other, and none other than Qodec also made one! Check out the link above, its been updated with these new puzzles :D
on 12. October 2025, 00:18 by chrisj50
I’m a bit rusty, but you’re clearly not! This was a lovely solve - really clean grid, felt very sparse to start but I enjoyed gradually realising all the implications of the renbans, and even then it was pretty tough! Hope you’re keeping well & thanks for another great puzzle!
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Second try at a reply -- thanks again for the kind words, glad you had fun with the puzzle, and talk to you over on Discord! :D
on 9. October 2025, 21:39 by earthpuzzles
So fun! I really appreciated how the rules interacted here. Simple yet complex, in the best way!
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Thanks a lot for the kind words, happy you had fun with it! This one might actually have a segue if the idea I had doesn't fight me too much, which would postpone my extended hiatus by one more puzzle, we'll see!
on 6. October 2025, 15:53 by Qodec
What a cool ruleset. Enjoyed that a lot!
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Thrilled to hear that Qodec, glad you enjoyed the puzzle, and many thanks for sharing! As for the ruleset itself, we have Sktx to thank for that one :D
on 4. October 2025, 17:27 by bodemeister
Of course there has to be a nice deadly pattern to make me fully solve the puzzle, not like the long solution code would also ensure this! Thanks as always for a great puzzle, and a nice dessert after testing your new doppelganger.
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Hehe, yeah, even if there hadn't been any new Still Life puzzle in a while, the ruleset had to 'still' somewhat be fresh in your mind after that crazy spring stretch of yours on that front, so it's no surprise your found this one to be a nice dessert XD Happy to hear you enjoyed it, and thanks for the kind words!
on 3. October 2025, 13:17 by zeniko
That‘s a nice combo of Game of Life and Renban, which would have had a nice flow if I wasn‘t so rusty with Conway‘s rules. Thanks for sharing.
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Thank you for the kind words, glad you enjoyed the puzzle! But it had been a while since the last Still Life puzzle, hadn't it, so it's no surprise that everybody's rusty. Plus I deliberately made the top half/close of the puzzle to be more Still Life intensive that the start, so well done getting through it despite the rustiness! :D
