Part of a series of examples. See:

1. [mousewheel-zoom + click-to-center via projection](http://bl.ocks.org/2206340)
2. [click-to-center via projection](http://bl.ocks.org/2206489)
3. [click-to-center via transform](http://bl.ocks.org/2206529)
4. [click-to-zoom via transform](http://bl.ocks.org/2206590)