Hard Calcudoku
Hard Calcudoku puzzles are 6×6 and need a naked or hidden triple or an X-Wing: a digit that fits only two cells in each of two rows, in the same columns.
Hard puzzles need at least one of these techniques, and may use any easier one:
- Naked triple
- Three cells hold only three digits between them, so those digits leave the rest of their area.
- Hidden triple
- Three digits fit only in the same three cells, so those cells hold nothing else.
- X-Wing
- A digit is limited to the same two columns in two rows (or the reverse), so it leaves the rest of those lines.
How to play
Calcudoku is an arithmetic logic puzzle on a square grid. Fill each row and column with the digits from 1 up to the grid's size, once each. Thick outlines group cells into cages, and each cage's digits must make the number in its corner using the operation shown: add, subtract, multiply or divide.
Every Calcudoku here has exactly one solution and can be solved by logic alone. The grid grows from 4×4 at Easy to 6×6, and the level is set by the hardest technique the puzzle needs.
- Each row and each column holds every digit from 1 to the grid size once.
- A cage's digits make its number with its operation: + adds, × multiplies.
- − and ÷ cages have two cells and work in either order, larger digit first.
- A one-cell cage simply shows its digit; digits may repeat within a cage if they are in different rows and columns.
Playing on this site
- Select a cell, then type a digit or tap it on the number pad. Arrow keys move the selection.
- Turn on Notes (or press N) to pencil in candidates instead of answers.
- Hint first points out any wrong digits, then names the next technique and shows where it applies before giving anything away.
- Your puzzle is saved in this browser, so you can come back to it later.