How to implement checkbox-like selection with client-side state & controls?

Hi,

This is my first Rails project, and I've just hit my first stumbling
block... I'm looking for some general pointers on how to implement the
following:

* Allow the user to toggle the selection of words in a given string
* Change the colour appropriately (ideally using CSS class)
* Prevent non-adjacent words from being selected
* Allow the user to submit the current selection

The text needs to read as a sentence, and I want to minimise server
involvement.

Is there anything in Rails or its plugins to help me out here, or is
pure Javascript the answer?

cheers,
Jon