Erm. Well, now Blogger is giving me an error, but hopefully this one works (from youtube).
To summarize though, the particles fire like a machine gun! Or maybe more like a Pew Pew Gun! Hmm. Must give that name more thought.
Also, muting with the M key, 3 dots stand for healthy, and you can just hold down left to shoot! Yes, the title says it all. But holding to left click has really made the default shooting more interesting, as you can now essentially move the particles around like with the right click, except now they deal damage too! Hooray!