The Doppit Almanac · No. 32

Cageit, a free daily killer sudoku

Cages sum to their number, no repeats

What it is

Cageit is killer sudoku. It plays like ordinary sudoku, so every row, every column and every box still holds each number exactly once. On top of that the grid is carved into dashed cages, and each cage carries a small corner number its digits must add up to. A digit never repeats inside a cage.

The only arithmetic is addition, and it is always in service of the logic: a cage of two cells summing to two rooms with no repeat can only be certain pairs, and that narrows the digits around it. Every board has one solution, reachable by reasoning rather than trial.

How it plays

• Fill every cell so each row, column and box holds every number once.
• Every cell sits in a dashed cage. The cage's digits must add up to its corner number.
• No digit repeats inside a cage.
• Pick a number chip, tap a cell to place it, tap again to clear it.
• Notes pencils small candidates while you narrow a cell down.
• A digit that breaks a house or a cage glows red. Stuck? Hint names the next step.

The difficulties

Easy is a six-wide grid that opens with most of its numbers already down, and its cages hand you another as soon as all but one of their cells is filled, a gentle half-minute solve. Medium keeps that six-wide grid but opens with eight to twelve numbers, so the cages carry far more of it. Hard is the classic nine-wide killer, where cage sums and the usual locked pairs work together. Expert is nine-wide, can open with no free numbers at all, and asks for eliminations hard never reaches: a locked triple, or a cage that pins a number to one line. A fresh board is dealt every day, for nothing. The dailies stop at hard, and expert is practice.

Nearby in the almanac: Summit, Digit and Plotit