Calcudoku

How to Play Calcudoku

Calcudoku (計算數獨) is a Latin-square arithmetic puzzle. Fill the N×N grid with the numbers 1 to N so that each number appears exactly once in every row and every column — the same no-repeat rule as Sudoku. The grid is also carved into bold-outlined groups called cages, and each cage shows a target with an operation in its top-left corner: the cage's cells must combine to that target under that operation. "6+" means the cells add up to 6; "8×" means they multiply to 8; "2−" (two cells) means their difference is 2; "3÷" (two cells) means one divided by the other is 3; a lone number is a free given. Click a cell to select it, then tap a number on the pad or press its key; use erase (or Backspace) to clear. Every puzzle here has exactly one unique solution, so careful logic always beats guessing.

Solving Techniques

• Single-cell cages are free: A cage with one cell just gives you that number outright. Place every given first — they instantly remove a candidate from their whole row and column.
• Forced combinations: Many cages allow only one set of digits for their size and range. In a 4×4, a two-cell "7+" must be {3,4}; a two-cell "12×" must be {3,4}; a two-cell "3÷" must be {1,3} or {2,6}-if-in-range. List a cage's legal digit sets, then let the row/column rule pick between them.
• The row/column total: Every row and column of an N×N grid sums to 1+2+…+N. When cages line up neatly with a row or column, that fixed total pins down a missing cell — a direct, no-guess deduction (the Calcudoku version of Sudoku's counting).
• Pencil the candidates: For each cell, track which digits its row, column and cage still allow. As you place numbers, the no-repeat rule and each cage's arithmetic prune the lists, and forced cells reveal themselves in a chain.
• Parity and factors: Product cages point straight at factors — a "15×" cage needs a 3 and a 5, a "1×" cell must be 1. Sum-cage parity (odd/even) narrows options fast. Anchor the grid on these tightly-constrained cages first, then let their digits propagate.

How do you solve Calcudoku faster? Fill the single-cell givens, crack the cages with only one possible digit set (small products and extreme sums), pencil in candidates, and cross-reference the row/column no-repeat rule until forced cells cascade. Because every valid Calcudoku has a single solution, every number you place should be one you can justify — no guessing required. The leaderboard ranks solves by completion time, so the fastest, cleanest logical path wins.