Do you need to know how to create the slapper, or just the particles? Or both? Do you want to create the slapper in-game, or through code? I would just create it in-game, and have a sort of extension to Slapper that listens to SlapperCreationEvent, and then create the particles with the plugin, assuming that event is also run when the plugin starts. By circular, do you mean a sphere or a spiral, or just a single circle around the middle of the slapper, etc.?