Queens

five queens. none may see another.

place 5 non-attacking queens on a 5×5

Five queens have to share a 5×5 board without any two attacking along a row, column, or diagonal — the same constraint chess players know from the eight-queens problem, just smaller. There are exactly ten arrangements that satisfy it, and finding one is the whole game.

Concepts: logic, constraints.

An interactive you play with one thumb, on Wundr.