original example by Karsten Schmidt
Toxiclibs ported to js by Kyle Phillips

Usage:

- Click the mouse to lock/unlock the end of the string at its current position.
- The head of the string is always linked to the current mouse position

Thread demo showing the following:

- construction of a 2D string made from particles and springs/sticks using the toxi.physics2d.ParticleString2D class
- dynamic locking & unlocking of particles