THE SHORT VERSION
If you've solved enough Sudoku that the easy ones feel automatic, the useful question isn't “what's harder.” It's what you actually enjoy about Sudoku — the pure logical deduction, the feel of numbers clicking into place under constraints, or the spatial pattern-hunting. Each one points to a different next puzzle, and GridJoy has seventeen others. Here's how to choose.
IF IT'S THE PURE DEDUCTION YOU LOVE
What Sudoku does best is force one logical answer out of constraints — no guessing required. Several puzzles are built on exactly that feeling.
Killer Sudoku is the closest jump: the same 9×9 grid and one-of-each rule, but the starting digits are replaced by cage sums. Pure deduction with an arithmetic on-ramp. Hitori flips the idea — instead of filling cells you shade them out, letting the no-touch and connectivity rules force every move. Takuzu (also called Binairo or Binary Puzzles) is Sudoku stripped down to two digits: no three in a row, balanced counts, every line unique. And Skyscraper keeps the Latin-square grid but adds visibility clues around the edges — you deduce heights from what you can and can't see.
IF IT'S PLACING NUMBERS BY ARITHMETIC
If the part you like is numbers settling into the only place they can go, lean into the arithmetic family. Calcudoku (also known as KenKen or Mathdoku) is a Latin square where each cage gives a target and an operator — fill the grid so every cage's math works out. Kakuro is a number crossword: fill runs of cells so each sums to its clue with no digit repeating — Sudoku's logic in a crossword's shape. And Killer Sudoku sits right between the two: Sudoku's grid, Calcudoku's cage arithmetic.
IF YOU WANT SOMETHING MORE SPATIAL
Sometimes you want the same single-solution rigour with less grid-scanning. Shikaku asks you to divide the board into rectangles — one clue per rectangle, equal to its area — so you factor, place, and eliminate. The wall mazes — Hex Mazes, Square Maze, and Circular Maze — drop numbers entirely: thread open passages from start to end by deduction, pruning dead ends rather than guessing. And Starlink and Inequality (Futoshiki) add a new rule on top of the Latin-square feel if you want to stay close to home.
THE HONEST ANSWER
Try two or three. The fastest way to find your next favourite is to play a first puzzle of each back to back and notice which one you don't want to put down. They all keep Sudoku's core promise: one logical solution, reachable without guessing, generated fresh every time so you never solve the same board twice.
GridJoy puts all eighteen in one app — free, fully offline, and with no ads mid-puzzle. If you just want to keep the daily habit while you explore, the free daily Sudoku runs right in your browser. Start there, then wander.