function animacion() {
	var cad = new Chain();
	
	var duracion = 1000;

	var entrar = function()
	{
		switch(n)
		{
			case 1:
				$('b1').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 0, 1);
				break;
			case 2:
				$('b2').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 0, 1);
				break;
			case 3:
				$('b3').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 0, 1);
				break;			
			case 4:
				$('b4').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 0, 1);
				break;
		}
		
	};
	var salir = function()
	{
		switch(n)
		{
			case 1:
				$('b1').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 1, 0);
				break;
			case 2:
				$('b2').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 1, 0);
				break;
			case 3:
				$('b3').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 1, 0);
				break;			
			case 4:
				$('b4').set('tween', {duration: duracion, transition: 'linear'}).tween('opacity', 1, 0);
				break;
		}
	};
	var aumentar = function()
	{
		n = n+1;
		if(n>4) n = 1;
	};
	cad.chain(salir());	
	cad.chain(aumentar());
	cad.chain(entrar());
	cad.callChain();
	cad.callChain.delay(10000, cad);
	cad.callChain.delay(20500, cad);
}