Daily math crosswords: grids of crossing equations

A math crossword swaps the clues and words of a crossword for equations. The grid has rows and columns of sums that cross each other, a few numbers are given, and every number you place has to make both its row and its column correct. Crossnum is one of these, with a new numbered grid each day at 2:00 AM local time that uses all four operations and keeps every step to whole numbers. Its puzzles start easy on Monday and get harder until Sunday, and you can go back to earlier days of the current week.

If you want the same thing in another place, start with Cross Math on Logic Puzzles Online. Its board is laid out like a crossword with the signs and results already in place, and you type digits into the gaps; there is one Daily grid plus Easy, Medium and Hard grids to play any time. Math Slide from PEMDAS Games changes the input: instead of typing, you drag tiles from a bank, each tile is used once, and your solving time is ranked on that day's leaderboard. Crucimates on La Vanguardia's games page, in Spanish, works the same way on an 11 by 11 board: you place number tiles in the empty squares, correct sums turn green and wrong ones red, and the game shows the share of players who solved the day's grid. On iPhone and iPad, Puzzle Math: Cross Number Game has a Daily Challenge calendar with a new dated grid each day; it is free with ads and in-app purchases.

Two more change what you have to work out. MathGrid on PuzzleMadness leaves both the numbers and the signs in a pile under the grid, so you also decide which operation goes where; it posts five grids a day, from Easy to Tough plus a Mixed one. SOLVD is an iPhone app with three small grids of linked equations a day, Easy, Medium and Hard, generated from the date so every player gets the same three.

MathemaGrids on BrainBashers is much smaller: a 3x3 grid where the digits 1 to 9 each go in once and the rows and columns are worked strictly left to right and top to bottom. It posts three grids a day, each with optional starting hints, which makes it a short warm-up rather than a full puzzle. SetSquare on PuzzleMadness works the same way, 1 to 9 once each with every line worked left to right and top to bottom, at several difficulties a day.

Kakuro, also called cross sums, is the number crossword that came before these. There are no operators to read: each run of white cells must add up to the clue at its start, using 1 to 9 with no digit repeated in the run. It rewards the same crossing deduction as Crossnum but with sums only. Play Kakuro and PuzzleMadness each post several sizes or levels a day with an archive, SudokuWiki numbers and grades its daily kakuro, puzzle-kakuro.com has a Special Daily Kakuro, Kakuro Haven is an app with its own daily grid, Sums on Mind Loft is a free daily one that is 7x7 on weekdays and 11x11 on Sundays, the Daily Mail posts a dated kakuro too, GridJoy has a Kakuro among its 18 free daily boards, Gamebox has a daily Kakuro beside three other logic puzzles, seeded from the UTC date, and the Telegraph's numbered daily Kakuro needs a Telegraph Puzzles subscription. The Daily Mail's Cross Number is a number crossword in the older sense: a crossword grid whose answers are numbers, with crossing entries sharing digits.

If you would rather guess a hidden equation in a few tries than fill a grid, see our guide to games like Nerdle (/games-like-nerdle). Cage puzzles such as KenKen, where groups of cells must reach a target with a given operation, are in our daily arithmetic games category (/daily-arithmetic-games). GridJoy's Number Crossword is not covered here: its runs are across only, so no number has to work in two directions.