Apple Motion 2 Tutorials - Manual (Page 206)

206 Tutorial 4 Working With Particles
12 In the Canvas, drag the Stars emitter toward the bottom-right of the Canvas.
13 Save your project (Command+S).
Adding a Simulation Behavior
Simulation behaviors are a shortcut to creating effects that would be extremely time-
consuming to keyframe. Adding a single
Simulation behavior can change a project
dramatically. One such Simulation behavior is Edge Collision.
To add Edge Collision to the particle emitter:
1 In the Layers tab, select the Stars emitter.
2 In the Library tab, select Behaviors, then select Simulations.