PPB has several ways to mark time: fixed-rate updates, frames, and idle time. These are all exposed via the event system.
ppb.events.Update event is fired at a regular, fixed rate
(defaulting to 60 times a second). This is well-suited for simulation updates,
such as motion, running NPC AIs, physics, etc.
ppb.events.Render are fired
every frame. This is best used for particle systems, animations, and anything
that needs to update every rendered frame (even if the framerate varies).