A particle mace sounds like a jolly fancy weapon, if a bit impractical. All those particles, roiling around, obeying only their own subatomic whims.
I was going to run a little further with that intro but it's a long while since I studied the sciences, and apparently years of reading xkcd has equipped me very poorly for understanding articles about the behaviour of particles. So that's all you get from me.
However, from a man named Andy Wallace you get the game of the same name: a 1-4 player arena shooter affair with a physics engine instead of boring old guns.
The trick, it would seem, is to use the particle mace that is dragged behind your ship to wallop your opponents as well as the numerous hazards scattered about the game's levels. It's all about momentum and inertia; your ship is extremely fragile whereas the particle mace that swings along behind you is just perfect for smashing things.
As for the longevity question: you've got 3 different arcade modes, 150 different missions, 9 unlockable ships, and of course those aforementioned multiplayer modes (both competitive and co-op - hurrah). There's also support for colour blind players, which is an excellent thing indeed.
Particle Mace has garnered a bevy of plaudits from various game festivals including Indiecade, Magfest, Gamercamp and Out of Index. Hopefully it'll prove as popular amongst groups of friends determined to smash one another with physics. It's out now on Steam with a 25% discount on its usual £5.99/$8.99/€5.99 pricetag, or directly via the official site.