Logic Puzzles

Every puzzle has exactly one solution

That sounds obvious and it is not. A logic puzzle with two valid solutions is broken, a solver who reasons correctly can still be marked wrong, which teaches the opposite of what the puzzle is for. Generating puzzles that are genuinely unique is harder than generating puzzles that merely look plausible, so the generators here run a solution counter over each puzzle before it is issued and discard any grid that admits more than one answer.

Every puzzle prints with its full solution on a separate page, so a sheet can be set as independent work and checked afterwards without you solving forty grids by hand.

Which puzzle for which solver

Sudoku is the usual entry point, and the 4×4 and 6×6 variants exist because the standard 9×9 grid is genuinely too much for a young solver, the smaller grids use the same logic in a form that can be finished in a few minutes. From there, the sudoku variants change the constraint rather than the size: diagonal, irregular, killer, arrow, thermo, word sudoku and the very large samurai grid.

If sudoku does not land, the deduction is often the problem rather than the numbers. Nonograms reward pattern reasoning and produce a picture at the end, which keeps solvers going. Hashi, slitherlink, masyu, numberlink and nurikabe are drawing puzzles where the answer is a route or a region, not a digit. Kakuro, KenKen and calcudoku bring arithmetic back in for anyone who wants the sums to matter.

The logic grid puzzles are the closest thing here to a reasoning test in the traditional sense: a set of clues, a grid of possibilities, and a single consistent assignment to find. They suit older solvers and work well as a group activity on a whiteboard.

Using them in a classroom

Logic puzzles are unusually good as settling work, because they are self-checking and quiet, and because a solver who is stuck is still reasoning. Printing a mixed pack across two or three difficulty rungs lets a whole class start at once without anyone being handed something obviously too easy. Magic squares, number pyramids and sequence puzzles are the gentlest options and work as a warm-up for the harder grids.