Extensions allow you to connect to hardware devices or web services. To add an extension, go to the More Blocks palette.
You need a plug-in to use any hardware extension. Download and then open the installer file for Mac or Windows. You will need administrator access on your computer to install it. (A Unix version will be available soon.)
Red light means that the browser plugin has not been installed.
Yellow light means that the device is not connected or detected.
Green light means the device is ready to go!