The 'Play' button is something we'd already implemented in a previous prototype, but it wasn't ready enough to be included in this release. It will show up in a future release though. :)

Also, by _slow_, were you referring to the actual rendering of the network when you adjusted the time-slider? Or the initial loading of the network itself? Because the former is actually pretty fast (if you are using Chrome), and the latter is something that we've tried to optimize as much as possible, but there are limitations.

The latter. Have you seen this tool? https://github.com/mbostock/d3/wiki/Force-Layout Try e.g. the 'build your own' demo, and add a few hundred nodes. There are quite a few demos out there using this layout and canvas, SVG, etc, that perform extremely well. Otherwise, further in the past I've seen some that offload calculation onto a webworker pool, some of them handling several thousand nodes (not all tightly connected, but still) without noticeably delaying the page. But I can't find those at the moment :/

Without profiling, I'd guess the biggest speedup is from the Barnes-Hut approximation [1], which is simple enough conceptually that you might even be able to implement it by hand (if you have control over your current layout algorithm).

[1]: http://en.wikipedia.org/wiki/Barnes%E2%80%93Hut_simulation

edit: hm, and it's noticeably quicker in Chrome than Firefox. That's a little surprising, given that I'm running the nightly build, and it's usually competitive :/

edit2: ah, you are using that. strange... I wonder where the slowdown is.