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+--- Thema: Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) (/showthread.php?tid=2461)
Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) - Todd - 01.07.2026
Hello, I'm the solo developer behind Spectradoku, a free browser-based Sudoku variant I've been building over the past months.
I'd love to share it with you and hear what you think.
── What it is ──────────────────────────────────────────
Spectradoku is Sudoku with two layers stacked together. Every cell holds both a digit and a color, and three rules apply:
1. Digits 1–9: each row, column, and 3×3 box contains each digit exactly once. (Standard Sudoku.)
2. 9 colors: each row, column, and 3×3 box contains each color exactly once. (A second Sudoku, on the color layer.)
3. Across all 81 cells, every (digit, color) pair appears exactly once — the two layers are mathematically orthogonal.
In combinatorics this is called a Graeco-Latin square. In play, it feels like solving two interlocking Sudokus at the same time, where each layer constantly informs the other.
── What makes it different ────────────────────────────
• A genuinely new puzzle type, not a reskin. The orthogonality constraint creates deductions that don't exist in standard Sudoku.
• Pure logic, no guessing. Every puzzle is verified solvable by human techniques alone — no bifurcation or trial-and-error needed.
• Five difficulty tiers, from a gentle Intro that teaches the two-layer notation, up to Expert puzzles that take 30+ minutes even for experienced solvers.
• Built for everyone. Works on phone, tablet, and desktop. Notes mode, eraser, hints, undo, and per-puzzle auto-save are all in.
• Completely free. No signup, no paywalls. Plays instantly in any modern browser.
── Try it ──────────────────────────────────────────────
https://spectradoku.com
If the Intro tier feels too easy after a puzzle or two, jump straight to Expert — that's where the variant really opens up.
── If you'd like to cover it ──────────────────────────
I'd be delighted to support coverage in any form: a written review, a video walkthrough, a social post, or a community feature. I can also create custom puzzles tuned to a specific theme, difficulty, or solving technique if that would help your content. No expectation either way — even just trying a puzzle and sending back a one-line reaction would mean a lot.
Thanks for taking a look.
RE: Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) - Realshaggy - 02.07.2026
Just a little puzzle from 17 years ago.
https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000012
RE: Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) - Todd - 02.07.2026
(02.07.2026, 13:22)Realshaggy schrieb: Just a little puzzle from 17 years ago.
https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000012
Thanks for the heads-up! You're right — this isn't a revolutionary sudoku variant, and the puzzle you shared follows the same logic as mine. That said, in my puzzles the clues are always given as number + color pairs, which makes them a bit harder to construct. I also went with the seven rainbow colors plus black and gray — easier for players to remember, and more visually appealing. Thanks again for the feedback!
RE: Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) - Realshaggy - 02.07.2026
Last time I tried, I didn't have much problems remembering the digits from 1 to 9.
RE: Spectradoku — a new Sudoku variant with two orthogonal layers (digit + color) - Todd - 07.08.2026
(02.07.2026, 14:11)Realshaggy schrieb: Last time I tried, I didn't have much problems remembering the digits from 1 to 9.
Ha, fair point — remembering 1–9 was never the hard part. Sorry if that came across the wrong way.
I chose colors mainly for how the board looks and feels in a browser UI, not because a second digit layer wouldn’t work. Your older puzzle already shows the idea clearly with two number dimensions.
Thanks again for pointing it out — I learned something from the thread.