Technique Hub
This page is the internal hub for long-tail technique queries. It gives Sudoku Evil a dedicated destination for players searching terms like X-Wing sudoku, Swordfish sudoku, and XY-Wing sudoku.
Use this hub as the map, then open the focused guides when you need a deeper explanation of a specific pattern.
X-Wing appears when a candidate is restricted to the same two columns in two different rows, or the same two rows in two different columns. That rectangle lets you eliminate the candidate from the overlapping lines outside the pattern. Read the full X-Wing sudoku guide for the scan checklist.
Swordfish is an expansion of the X-Wing idea across three rows and three columns. It is rarer, but it becomes much more relevant in evil sudoku where the board stays crowded longer. The Swordfish sudoku guide explains when to escalate from two-line to three-line patterns.
XY-Wing uses a pivot cell and two wing cells to prove that one candidate can be removed from a shared peer. It is useful when bivalue cells begin to dominate the remaining grid. Open the XY-Wing sudoku guide when a puzzle has many two-candidate cells.
XYZ-Wing is related to XY-Wing but uses a pivot with three candidates. It can create a strong elimination in positions where the candidate network is dense but structured.
Forcing chains test what happens under linked assumptions. If every branch of a chain leads to the same conclusion or contradiction, you can eliminate candidates confidently without blind guessing. The forcing chains guide covers this late-game logic in more detail.
On many hard boards, the solve flow looks like this:
That is why a technique hub works well alongside a live game page. Users can study a pattern, then immediately return to a puzzle and apply it.