Finishing Pong: Scoring and Game Interaction - Learn GameSalad for iOS: Game Development for iPhone, iPad, and HTML5 - page 72

Drag a Change Attributebehavior into the Ball Detection rule. Set
game.P1Serving to 0, as in Figure 3-9.
Figure 3-9. Change P1Serving to false
About Boolean:
Boolean attributes are true/false attributes. To save a little bit of time,
you can substitute true and false with 0 and 1, respectively.
GameSalad will automatically associate 0 to false and 1 to true
Repeat the operation with the Right Winning Zone; this time game.P1Serving
must be set to 1, as in Figure 3-10.