The Doppit Almanac · No. 05

Duoit, a daily binary puzzle

Equal suns and moons, no three alike

What it is

Duoit is Doppit's daily binary puzzle, a strict balance of two symbols. It sits at No. 05 in the almanac. Suns and moons divide a grid in strict parity: day and night stay even in every line, and no streak may reach three.

Some cells come printed. Bridges between neighbours add small contracts of their own. The rules fit on a matchbook, and the consequences do not.

How it plays

Three laws govern the grid, and the board itself keeps the ledger.

• Every row and every column holds the same number of suns as moons. Day and night balance line by line.
• No three alike ever stand together, across or down. Two of a kind is company, three is a violation.
• A bridge marked = chains two neighbouring cells to match. A bridge marked × obliges them to differ.
• Grey pieces come printed on the board. Break a rule anywhere and the offending cells glow red until you mend them.

The difficulties

The daily run comes in three sizes. Expert is a fourth, kept back for practice. Easy is six wide and balances out in thirty seconds to a minute. Medium is eight wide and wants one to three minutes. Hard is ten wide and runs three to six, and by the end you will be counting moons in your sleep. Expert is twelve wide, the largest grid Duoit builds, and it wants the same suppose-and-check step hard does across every one of those rows and columns. A new grid rises every day, and it costs nothing.

Nearby in the almanac: Yinit, Rankit and Nonit