Thanks. I'm glad you enjoy it.Slowness
The decrease in speed isn't from drawing the particles as much as it is calculating their new velocities and positions.Why is it slow?
Every body with mass effects every other body in a system so a system with 10 bodies with mass requires (10x10=100) gravity calculations per step. Each particle is influenced by every body with mass: Bodies with Mass x Particles in Ring x Multiplier (10x200x20=40,000 calculations per step). Adding a single body with mass increases the calculations dramatically (11x11=121 and 11x200x20=44000). If you turn down the particle multiplier then the numbers get a lot lower (11x200x2=4400)
If you pause the simulation these calculations are not performed and the frame rate goes up.Short Answer
Your experience is about what I get on my development machine, so just turn the particle multiplier back down. Why allow such high values?
It's possible to turn up the particle multiplier higher than the fastest computers can support in real time. The high values are for fast computers in the future and non-real time movie capture.
I'm not currently supporting the Ageia PhysiX Accelerator, but is something I may look into in the future.