download these 39KB JS package from https://github.com/subprotocol/verlet-js
and open offline the file index.html then run one of these:
Shapes (verlet-js Hello world)
Fractal Trees
Cloth
Spiderweb

i prefer Spiderweb, it is a great simulation of a spider and its web, you can also run it online http://subprotocol.com/system/spider.html
but the offline version can run even on the oldest browsers such as my opera portable v11.61 on windows xp