Hyper Sudoku — also called Windoku — plays like classic Sudoku, with four extra 3×3 regions on top of the standard ones. Every row, column, and 3×3 box still holds each digit 1 through 9 exactly once; on top of that, each of the four hyper regions (one inset from each corner of the board) also holds every digit 1 through 9.

The hyper regions are marked with solid coral outlines so they're clear at a glance. They overlap with the standard 3×3 boxes, so a digit placed inside a hyper region constrains two regions at once.

The extra rule is more powerful than it looks. A hyper region spans across the boundary of two standard boxes, so a digit blocked from one half of the region by a row or column hit is forced into the other half — even when the standard box scan didn't make that obvious. When a puzzle feels stuck on standard scanning, the hyper regions are usually where the next deduction lives.

Expert puzzles demand advanced techniques: swordfish, XY-wing chains, unique rectangles. A correct solve at this level rewards patience more than speed.

The timer is for you, not for us. Fewer than twenty minutes on an expert puzzle is very good; under ten is exceptional.