The keyTracker is just a way to access which key are pressed during a callback instead of through events. To enable it you just specify the option keyTracker: true in the .playground() function. Then at any moment you can simply use the array $.gameQuery.keyTracker to access the state of the keys, for example: since 65 is the keycode for 'a' you can check the value of $.gameQuery.keyTracker[65] and if it's true then the 'a' key is pressed!

But no the mouse is not supported there, thought it is a very good idea and a simple one to implement, I will add it to the list of new feature for gQ 0.7!