What "SE-compatible" means
Sudoku University rates every puzzle using an original weight table, built from scratch by studying publicly documented technique explanations and calibrating the results against the community-standard Sudoku Explainer (SE) difficulty scale that most Sudoku players already recognise.
No code, weight tables, or internal values from any existing Sudoku Explainer implementation were copied or ported. The rating engine is described as SE-compatible, or based on the community-standard SE scale. It is never presented as the official Sudoku Explainer rating, because it isn't one: it's an independent engine designed to land in the same neighbourhood as the scale most solvers already use to talk about difficulty.
The six difficulty tiers
Every puzzle is solved with the full technique ladder before it's ever shown to you, and its tier is set by the hardest technique genuinely required to finish it, not by an arbitrary numeric target.
| Novice | Full House, Naked Single, Hidden Single: the fundamentals every solver starts with. |
|---|---|
| Easy | Locked Candidates (Pointing & Claiming), Naked Pair, Hidden Pair. |
| Medium | Naked/Hidden Triple & Quad, basic Fish (X-Wing), Simple Coloring. |
| Hard | Swordfish, Jellyfish, XY-Wing, XYZ-Wing, W-Wing, Skyscraper, 2-String Kite, Empty Rectangle, Unique Rectangle Types 1–2, BUG+1. |
| Expert | X-Chain, XY-Chain, Multi-Coloring: the longer logical chains that link several regions together. |
| Master | Reserved for puzzles the technique ladder can't crack. Solved only by a backtracking/DLX search, used purely as a fallback validator rather than a technique you're taught. |
See the Technique Glossary for a full explanation of every technique named above.
How puzzles are generated
Puzzles aren't picked from a fixed library. They're generated fresh and checked at every step. The generator digs clues out of a completed grid one at a time, confirming after every removal that exactly one solution still exists. Once digging stops, the puzzle is solved end-to-end with the same technique ladder the hint engine uses, confirming it's genuinely solvable within its intended tier before it's ever served to you.
A note on honesty
Is this the official Sudoku Explainer rating? No. It's a from-scratch engine, built independently from public documentation, calibrated to land close to the scale most Sudoku communities already use, described honestly as SE-compatible so you know exactly what you're getting.