Crossnumbers
What is Crossnumbers?
Crossnumbers is a free number puzzle that trains logical thinking the same way a crossword or sudoku does, but with digits instead of letters or fixed regions. Every space in a 15x15 grid needs a number from a given list, and every number is used exactly once — the only way in is by cross-referencing the digits that two intersecting numbers share, so the puzzle rewards deduction over guessing. It belongs to a small family of puzzles sometimes called "fill-ins" or "number crosswords," long used as a quick, low-pressure way to exercise logical reasoning and short-term memory on a break.
How to play Crossnumbers
Fit every number from the bank on the right into its matching space in the grid. Each space's length tells you which numbers can go there — the puzzle is solved by cross-referencing the digits that intersecting numbers share, the same logic that makes a crossword or a sudoku click into place.
The rules
Every open space in the grid needs one number from the bank, and every number in that bank is used exactly once, in exactly one space. A number can only go in a space with the same number of digits — a 5-digit number fills a 5-digit space, never a 6-digit one. Numbers cross at shared cells, and the shared digit has to be correct for both the horizontal and vertical number meeting there — that overlap is the actual puzzle.
How to place a number
- Click or tap a cell to select it, then type a digit — the cursor moves to the next cell in that space automatically.
- Press D, or click a cell you've already selected, to switch between its horizontal and vertical space when a cell belongs to both.
- Use the arrow keys to move around the grid without leaving the keyboard.
- Backspace clears the current cell, or steps back into the previous one and clears that instead if the current cell is already empty.
Reading the grid as you go
One full number space starts already filled in and checked off the bank — a solved starting point to build outward from, not a scattered hint. As you fill a space, its digits are checked against the bank: if what you've typed doesn't match any number of that length, the space is marked as a conflict until it's fixed. The number bank on the right crosses off every number you've correctly placed, so its count doubles as a running progress check.
Tips for solving faster
- Start from the one revealed number and work outward through everything that crosses it — a known digit rules out most candidates for the crossing space immediately.
- Place the longest numbers first. A 10-digit number has far fewer possible candidates than a 4-digit one, so it narrows the puzzle down faster.
- When two spaces of the same length are both still open, check what's already fixed at their crossings before guessing between the numbers left in that group.
- Use Check whenever you're unsure — it counts correct, empty, and conflicting spaces without giving away which number goes where.
Free play, Daily Challenge, and Relaxed mode
Free play generates a brand-new 15x15 grid from a random seed every time — no two puzzles are the same. Daily Challenge loads the same puzzle for everyone, on that day, wherever they are — a good one to compare notes on. Relaxed mode turns off the timer entirely, so nothing is being measured while you play; turn it off if you'd rather have the clock running and a finishing time to compare.
How this puzzle works
Every grid is generated and solved entirely in your browser — nothing is uploaded, and no server is involved at any point during play. Your progress, timer, and settings are saved locally, so closing the tab and coming back picks up exactly where you left off.
Frequently Asked Questions
Is Crossnumbers actually good for your brain?
Puzzles like this one exercise working memory and logical deduction — the same skills used in solving a crossword or sudoku — by asking you to hold several possibilities in mind and narrow them down using digits already on the board. It's a light mental workout, not a substitute for anything else, but a genuinely useful way to spend a break.
Is my progress saved if I close the tab?
Yes. Your grid, typed digits, timer, and settings are saved in your browser and restored automatically the next time you open the game.
What's the difference between Crossnumbers and a regular crossword?
Same crossing-grid logic, but with digits 0–9 instead of 26 letters — which means far fewer valid options per space, so the puzzle leans more on elimination than on vocabulary.
Why can't I edit some cells?
One full number is revealed at the start as a solved starting point. Every other cell is yours to fill in, clear, and change as often as you like until the puzzle is complete.
How is the grid different every time?
Both the blocked-cell shape and every digit are generated fresh from a random seed for each new game, then checked to make sure the puzzle has exactly one valid solution before it's shown to you.
Can two puzzles ever have the same solution?
It's possible but astronomically unlikely — with a fresh random seed shaping both the grid's shape and its digits each time, the odds of two games matching are effectively zero.
What does the conflict warning mean?
It means the digits currently in that space don't match any number in the bank of that length — somewhere in that space, or one crossing it, has the wrong digit.
Can I share a puzzle with someone else?
Yes — Share seed copies a link that loads the exact same grid for whoever opens it, so you can compare notes on one specific puzzle with someone else.