Logic puzzles that reward patience, not luck — Sudoku variants, number-cages, region-shading and bridge-building, all free in your browser.
Every puzzle on this page is a true logic puzzle — one solution, always reachable by reasoning rather than guesswork. That single rule ties together puzzles that otherwise feel nothing alike.
You place numbers under constraints in Variant Sudoku and Suguru, work arithmetic cages in Calcudoku and Kakuro, shade islands in Nurikabe, or connect them up in Hashi. Each rewards a different habit of mind.
Grids scale from a quick 5×5 to a meaty 11×11 across seven levels — from Beginner, which leaves a few helping hints on the board, up to Cyborg, which leaves you nothing but the logic.
The single-solution rule is what these puzzles share. It is not what makes them feel different from each other, and if you pick your next one by grid size you will keep landing on the same sensation. The real split is the shape of the deduction. Kakuro, Calcudoku and Mad Add are arithmetic puzzles — you are reasoning about sums and factors, and the grid is only where that arithmetic happens to live. Nurikabe, Hashi Bridges and Weave ZAP are geometric: their hardest rules are about connectivity, and what catches you out is a shape rather than a number. Takuzu, Suguru and Variant Sudoku are placement puzzles, where a symbol's whole job is to differ from its neighbours. Mirror Maze sits outside all three. You are not uncovering a hidden answer there, you are constructing one, and the beam redraws its entire path the instant you set a mirror down.
Takuzu. Two symbols, three rules, and you are solving within a minute of arriving. From there, Suguru's small cages teach the habit that carries every other board on this page — place a digit, then read the full ring of eight cells around it before you place another. Go to Kakuro if arithmetic is the part you enjoy, Nurikabe if you would rather think in shapes, and Mirror Maze if building an answer appeals more than deducing one.
Beginner, Easy, Medium, Hard, Very Hard, Scientist, Cyborg. In this genre they rarely mean more of the same. Kakuro is the clearest case: climbing the ladder makes the board emptier, not fuller. Black clue cells fall from roughly 40 per cent of the grid at Medium to about 32 per cent at Cyborg, while the longest run grows from five cells to nine. Fewer clues, longer runs, more combinations alive per clue — that is what hard buys you. And a constraint underneath pushes the same dial the other way. The ambiguity that costs a board its unique solution comes from small exchanges between crossing runs, and the number of places such an exchange can occur grows with the board's area. So a larger grid has to carry a lower density to stay uniquely solvable. Size and difficulty are not one axis here, which is why they are two separate dials.
Early Kakuro builds could hang the main thread for over a second while hunting a guaranteed-unique large board, and in a browser game a frozen second reads as a crash. So generation now runs against a wall clock: if the budget expires, the generator accepts a rare non-unique board at the same size rather than ever freezing. Nobody notices a second valid solution. Everyone notices a hang. Mad Add runs the same deal. Suguru is the honest edge case — that puzzle family genuinely admits boards with more than one valid arrangement, and I stopped fighting it. If you find a second answer that fills every region and never touches itself, you have not broken anything.