vector.js

var Vector = function(_x, _y)
{
	this.x = _x;
	this.y = _y;
	
	this.draw = function(size, color) {
		gfx.beginPath();
		gfx.arc(this.x, this.y, size, 0, 2 * Math.PI, true);
		gfx.fillStyle = color;
		gfx.fill();
		gfx.strokeStyle = color;
		gfx.stroke();
	}
	
	this.add = function( vector )
	{
		return new Vector(this.x += vector.x, this.y += vector.y);
	}
	
	this.subtract = function( vector )
	{
		return new Vector(this.x -= vector.x, this.y -= vector.y);
	}
	
	this.multiply = function ( multiplier )
	{
		return new Vector(this.x *= multiplier, this.y *= multiplier);
	}
	
	this.length = function()
	{
		return Math.sqrt(this.x * this.x + this.y * this.y);
	}
	
	this.cross = function( vector )
	{
		return this.x * vector.y - this.y * vector.x;
	}
	
	this.dot = function( vector )
	{
		return this.x * vector.x + this.y * vector.y;
	}
	

	
};