Abalone

Abalone is a thinking board game, sold up to 4 millions pieces in 30 countries. He was granted to the rank of the "Game of decade" at the "festival international des jeux" in 1998. Easy to understand, Abalone is universal with a simple goal: push 6 from 14 balls of the opponent from board according to numeric superiority principle.
Both players can displace 1, 2 or 3 balls at the most, on every turn, in a single stroke, in any direction.
To be able to push your opponent's balls, you need to have a numerical superiority : with 3 balls you can push 1 or 2 balls; and with 2 balls you can push 1.
But if the number of balls is the same on each side, it is impossible to push.

Simple? Certainly. Simplistic? By no means. For we all know that the possibilities of displacing balls, mounting attacks, organizing defences and combinations are endless and they are invariably strategic.