A particle can take its picture from a sprite sheet: atlas in the effect, then one frame by its place or its name, or an anim every particle plays from its birth. animPace: 'clip' plays the run at its own fps, as a sprite would: the fire on the left, from a .particles file naming an .atlas. animPace: 'life', the default, stretches it over each particle's life, so the explosion on the right starts as a flash and dies as smoke however long each puff lives.
The explosion's sheet is painted in pixels and its run written in code. The rocks are one frame each, with a tail that shows the frame its particle shows. Click to set one off.