Moving Lime shapes with keyboard

gistfile1.js

//set main namespace
goog.provide('keycontrol');

/**
 * Sample for using keyboard to naturally move around lime objects.
 */

//get requirements
goog.require('lime.Director');
goog.require('lime.Scene');
goog.require('lime.Circle');
goog.require('goog.events.KeyCodes');


// entrypoint
keycontrol.start = function(){

	var director = new lime.Director(document.body,1024,768),
	    scene = new lime.Scene(),
      circle = new lime.Circle().setSize(75, 75).setFill(255,150,0)

  var SPEED = 0.05, FRICTION = 0.95, MAXSPEED = 10;

  var ax = 0, ay = 0, vx = 0, vy = 0;

  goog.events.listen(goog.global, ['keydown', 'keyup'], function (e) {
    var isdown = e.type == 'keydown';
    switch (e.keyCode) {
      case goog.events.KeyCodes.LEFT:
        ax = isdown ? -SPEED : 0;
      break;
      case goog.events.KeyCodes.UP:
        ay = isdown ? -SPEED : 0;
      break;
      case goog.events.KeyCodes.RIGHT:
        ax = isdown ? SPEED : 0;
      break;
      case goog.events.KeyCodes.DOWN:
        ay = isdown ? SPEED : 0;
      break;
    } 
  });
    
  lime.scheduleManager.schedule(function(dt) {
		vx += ax * dt;
		vx *= FRICTION;
		vy += ay * dt;
		vy *= FRICTION;
    var pos = circle.getPosition();
    circle.setPosition(pos.x + vx, pos.y + vy);
  });

  scene.appendChild(circle);
	director.makeMobileWebAppCapable();

	// set current scene active
	director.replaceScene(scene);

}

//this is required for outside access after code is compiled in ADVANCED_COMPILATIONS mode
goog.exportSymbol('keycontrol.start', keycontrol.start);