harvesthq/chosen ? reverse-engineered prompt

Build me a front end library that makes long select boxes feel easy to use. I want a nice searchable dropdown that improves normal HTML select fields, so users can type to filter options, pick one or many items, and see the selection in a clean way. It should work with both jQuery and Prototype, and feel lightweight enough to drop into an existing site without much setup.

Please include the styling and behavior for the custom dropdown, keyboard support, and a simple demo page with a few examples for single select, multi select, and a long list of options. I also want the code organized so it’s easy to build, test, and package for download. If anything is unclear, look up current docs online if you need to.