Super Tic Tac Toe - Super simple strategy game

Looking for is a simple strategy game?

Simple games are easy to find, but they lack strategy. Search for strategy games and you lose simplicity.  Simple and strategy aren't two things you expect to find together.

But what if you can get both in one game just by introducing a new rule into a game which you already know.

Super Tic Tac Toe is such a game. It's like a widely-known Tic Tac Toe game with one additional rule, which is enough to give plenty of strategic depth without overwhelming a new player. 

Super Tic Tac Toe is a very-very simple (if not the simplest) strategy game.