An example Global Entropy puzzle: every 2×2 area holds all three groups - low 1-3 (blue), middle 4-6 (green), high 7-9 (red). Here 1, 5, 8, 3 covers all three.
Global Entropy Sudoku sorts the digits into three groups - low (1-3), middle (4-6) and high (7-9) - and adds one board-wide rule: every 2×2 block of cells must contain all three groups. With four cells and three groups, one group repeats, but none may be missing.
The rule: every 2×2 mixes the groups
Slide a 2×2 window anywhere across the grid. Wherever it sits, its four cells must include at least one low, one middle and one high digit. That single constraint threads eliminations through the whole grid, on top of the usual rows, columns and boxes.
Solving strategy
- Think in groups first. Often you can fix a cell's group (low/middle/high) before its exact digit.
- Watch overlapping windows. Adjacent 2×2 blocks share two cells, so one placement constrains several windows at once.
- Three into four. If a 2×2 already shows two groups, its remaining cells must cover the third.
Common mistakes
- Requiring one of each in four cells. Four cells, three groups - one group appears twice; only absence is forbidden.
- Checking only the box 2×2s. The rule covers every 2×2 window, including those that straddle box borders.
- Dropping ordinary Sudoku. Rows, columns and boxes still each need 1-9 once.
Can I play it here?
Not yet - Global Entropy Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Global Entropy Sudoku belongs to the constraint family and runs on 9×9. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Expert Sudoku leaves 25 of the 81 cells filled, where the beginner tools dry up almost entirely; Evil Sudoku leaves 23, with no easy moves at all. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.