getRandomNumber = function(max) { return Math.floor(Math.random()*max+1)-1};

ImageMorph.subclass('Mouse', {
howFarCanIGoWithOneStep: 5,
maxTurn: Math.PI/2,
initialize: function($super) {
	// call the initialize of ImageMorph with the mouse picture
	$super(new Rectangle(45, 45, 49, 49), 'http://www.lively-kernel.org/repository/lively-wiki/mouse.png');
	// move position to the center of the morph instead of top left corner, nicer rotating behavior
	this.moveOriginBy(this.getExtent().scaleBy(0.5));
	// remove the blue background
	this.setFill(null);
},
calculateNewPosition: function() {
	var p = this.getPosition();
	var angle = this.getRotation()+Math.PI*(1/2);
	var r = this.howFarCanIGoWithOneStep;
	return pt(p.x+r*Math.cos(angle), p.y+r*Math.sin(angle));
},
moveOneStep: function() {
	this.mayBeChangeDirection();
	var newPos = this.calculateNewPosition();
	while (!WorldMorph.current().bounds().containsPoint(newPos)) {
		this.newDirection(); 
		newPos = this.calculateNewPosition();
	}
	this.setPosition(newPos);
},
mayBeChangeDirection: function() { if (getRandomNumber(10) == 5) this.newDirection() },
newDirection: function() {
	this.rotateBy(getRandomNumber(this.maxTurn*100)/100 - this.maxTurn/2);
},
startSteppingScripts: function() { this.startStepping(20, 'moveOneStep') }
});