Greekest (Puzzleship)

Greekest asks for a Latin square with an extra twist: the two long diagonals count too. Every symbol has to appear exactly once in each row, each column and each of the two diagonals. Cells on a diagonal answer to three rules at once, and the centre cell, where both diagonals meet, answers to four.

It resembles diagonal sudoku but has no boxes, and the cells hold Greek letters such as alpha and omega rather than numbers. That removes any arithmetic habit and leaves a pure question of where each shape can still go. Asking where a symbol can go in a row is often more useful than asking what fits a cell.

Puzzleship publishes six grids of Greekest a day, graded from very easy to ultra hard. Each day's grids are numbered and dated, the same for every player, and go up at 13:00 UTC, although the page's countdown says 00:00 your time; earlier days stay playable in the archive. The site is free with ads, and a premium plan removes them.