Daily Kakuro — Free Online Puzzle
A shared 8×8 cross sums puzzle each UTC day.
How to play
Fill each white cell with a digit from 1 to 9. A clue in the top-right triangle gives the total for the white cells to its right. A clue in the bottom-left triangle gives the total for the cells below. Black cells separate runs. Never repeat a digit within one run.
Tap a white cell, then use the number pad or your keyboard. Its Across and Down totals appear above the pad. Notes toggle pencil candidates; Erase clears the selected cell, and Undo restores your last entry. Repeated digits turn red. A completed run with the wrong total has an amber outline.
Check compares entries with the answer. Show solution fills the grid and stops the timer without earning a daily solve. Reset clears the same puzzle. The timer starts with your first entry and stops when you solve. Share sends your time and puzzle link without any answer digits.
A short history
Cross sums puzzles have appeared in American puzzle magazines under the name Cross Sums. In Japan, the form became familiar as Kakuro. Nikoli records its introduction in issue 11 of its puzzle magazine. The intersecting runs make a small addition puzzle into a placement problem: a digit has to satisfy two totals at once. Read the puzzle history.
Code builds a connected black-and-white pattern, fills it by backtracking without repeated run digits, and derives the clues. A solution counter uses distinct-digit sum combinations and rejects every grid that has more than one solution. Search limits cause a retry or an error, never a uniqueness claim. The served page contains only the size, seed, black-and-white pattern and clues; the browser regenerates the answer for Check and Show solution. No model creates a puzzle.
Solving tips
Start with totals that allow only one pair: 3 in two cells = 1+2; 4 in two = 1+3; 16 in two = 7+9; 17 in two = 8+9. These tell you which digits belong in a run, but an intersecting clue decides their order.
Compare the candidates for both runs crossing a cell. For example, a cell in a two-cell run of 3 can only hold 1 or 2. If its other run excludes 1, it must hold 2. In a nearly filled run, subtract the entered digits from its clue and check that the remaining digit has not already appeared.
The 6×6 easy, 8×8 medium and 10×10 hard labels describe board size, not a measured solving technique. Sizes include the black clue row and column. Practice opens a fixed starting puzzle; New puzzle changes only the seed and share address in your browser. The daily is a shared 8×8 puzzle chosen by UTC date.
Progress, notes and time stay on this device. A daily streak counts consecutive UTC dates solved without revealing the answer. Replaying the same date adds no extra day. A dated share link keeps that puzzle available after midnight. There is no countdown, account or download.