You just judge ball or strike. There are two modes, simple or hard. In simple mode the strike zone is indicated on the screen and stays up through the pitch. In hard mode it disappears just before each pitch. I’m not sure the developer knows baseball though because the batter will swing and miss at a pitch outside the strike zone, yet it says you’re wrong if you correctly call it a strike. And that’s it for the gameplay, no base running or foul/fair calls.