Left paddle is controlled by W & S, right paddle by UpArrow & DownArrow. Check it out online and try to modify it yourself here. The easiest way to build crafty is to use gruntjs, which requires node and npm. If you have grunt, node, and npm already installed, then run npm install from Crafty's root directory. (This will pull down about 30MB of node packages.) From then on, just run grunt to build.