Ataxx

Ataxx (アタックス) is a strategy video game published in arcades by Leland Corporation in 1990. Two players compete on a seven-by-seven square grid. The object of the game is for a player to have a majority of the pieces on the board at the end, by converting as many of their opponent's pieces as possible. In a single-player game, the opponents are "bio-invaders from a different dimension."