Crossnum

Crossnum describes itself as a crossword without the words. Each day brings one numbered board of interlocking equations: rows and columns of numbers joined by plus, minus, times and divide signs, sometimes with brackets, each ending in a result. Some cells are blank, and your job is to fill them so every equation holds.

The rules keep the arithmetic clean. The range of allowed numbers is shown above the board: 1 to 16 for cells and 0 to 64 for results on 3x3, 3x4 and 4x3 boards, 1 to 32 and 0 to 128 on larger ones. Numbers you multiply and divisors cannot exceed 12, and every step must give a whole number of zero or more, so there are no fractions or negatives. Each puzzle has one solution, reachable by deduction alone.

A new puzzle arrives every day at 2:00 AM, and difficulty follows the week: a Monday or Tuesday board takes two to four minutes, a weekend one five to ten. A line is checked only once it is full, and a full line that does not add up counts as one miss. Your solve time ranks you among the day's players, with fewer misses breaking a tie.

The daily plays with no account, and a streak is kept on your device; an account carries it between devices. Every puzzle of the current week stays open, so Monday's board can still be played on Thursday, while older weeks are closed. After solving you get a challenge link that lets a friend play the same board and compare times, and you can follow friends to see their daily results. There is a tutorial and a practice game, a light and dark theme, and the site can be installed as a web app.

Crossnum now shares its home page at crossnum.com with Sufuku, a sudoku-like daily puzzle from the same site with the same 2:00 AM reset and weekly difficulty curve.

It suits people who like sudoku and kakuro and want a numbers puzzle that rewards careful logic rather than speed with mental arithmetic.