International Superstar Soccer 99 is a single-player sports game in which players simulate international soccer matches, managing teams and competing in various game modes. In this game, players take on the role of a soccer coach, selecting from 32 international teams to compete for the International Cup, with options to customize match length, overtime rules, and team strategies. It stands out with its detailed gameplay mechanics that include choosing lineups, formations, and tactics, providing a realistic soccer experience on the Game Boy Color, along with multiple difficulty levels to challenge players of all skill levels.