The Doppit Almanac · No. 25

Soloit, a daily Hitori

Shade the doubles so each number stands alone

What it is

Soloit is Doppit's Hitori, the Japanese puzzle of the crossed-out grid. The board opens full of numbers. You shade cells until every number still showing is the only one of its kind in its row and its column. Each survivor stands alone.

The turn of it is that you never write a number, you only strike them out. A row with the same number twice tells you one copy has to go, and the deductions cascade from there. Touching shaded cells and leftover repeats glow as you work, so a wrong move shows itself at once.

How it plays

The rules are three lines.

• No number repeats, unshaded, in any row or any column. A number may appear again only if one copy is shaded.
• Shaded cells never sit side by side. Corners are fine.
• The cells left showing all join up as one connected sheet.
• Circle marks are yours. They flag a cell you have proved must stay, and the win ignores them.

The difficulties

Four boards are posted daily. Easy falls in thirty seconds to a minute on a five by five grid. Medium is one to three minutes at seven by seven. Hard runs three to six minutes at nine by nine and saves a what-if or two for the finish. Expert stays at nine by nine and leaves fewer repeats to work with, so one what-if is no longer enough. You suppose a cell, follow the rules on from there, and have to suppose a second one before the first is settled. A fresh board arrives every day, and it costs nothing.

Nearby in the almanac: Islandit, Summit and Nonit