var timer;
var dx = 1;
var k = 50;
var p = 400;

function BirdFlies(){	
	var x;
	dx = 1;
	var re = new RegExp("[-]?[0-9]*");
	x = bird.style.left.match(re);
	
	if(x < -60){
		window.clearInterval(timer);
		bird.style.visibility="hidden";
		return;
	}
	
	x-= dx;
	y = (x - p)*(x - p)/1000 + k;
	
	bird.style.left = x + "px";
	bird.style.top = y + "px";
	
}



function bird_init(){
	timer = window.setInterval("BirdFlies()", 10);
}