This is where our tortoise lives!
NetLogo Web (formerly known as "Tortoise") is a JavaScript-based version of NetLogo that runs entirely in the client's browser. This repository is for the Play application that serves up NetLogo Web pages.
Related is Teletortoise, which allows you to use your browser to interact with an instance of classic NetLogo that is running on a server. You can check out Teletortoise here.
For more information about the NetLogo Web project in general, see here.