/**
    * Snake game to get more fluency programming in JavaScript.
    * The first two games I wrote I was learning googling and reading a lot.
    * After that I stopped writting code and started to study 
    * the book Javascript The Good Parts from Douglas Crockford. And when I
    * finished it, then I started to make this one, in a complete different 
    * way of coding. Just check the code of Space Invaders and then check this
    * one. I think this is more clean and professional, well documented following
    * JSDOC, and maybe using some of the best parts of this language. Carlos Benítez
    * from www.etnassoft.com helped me a lot "forcing" me to do the functions and 
    * methods in the correct way and to document it right. And also helped me solving
    * closures problems and hoisting problems.
    *
    * Current Status:
    * Playable. 
	* Increased performance by more than 50% using a buffer to draw
    * outside the canvas and then drawing on the canvas just the complete image
    * of the buffer. I'll use that on every game from now on.
    * Refactorized several things, trying to avoid some redraws, drawing just 
    * when needed.
	*
	* ToDo
	* · Solve Insane speed (SOLVED)
	* · If you continue when you lose 3 lifes, the game continue forever
	*     like if you had infinite lives (SOLVED)
	* · Try to catch more accurately the arrows (SOLVED MORE OR LESS)
	* · Show the Score and the lives during game(SOLVED)
    *
    * @author Sergio Ruiz
    * @version 1.1 01-05-2011 01:32
    */