function slider(opt,areaVisivel,direcao) {
	this.IdInterval = null;
	this.startScrollUp = function() {
		var sl = this;
		
		this.IdInterval = setInterval(
			function() {
				var margin = sl.Str2Int(direcao == "vertical" ? opt.style.marginTop : opt.style.marginLeft);
				margin -= 5;

				if(margin < sl.max)
					margin = sl.max;
				
				if (direcao == "vertical")
					opt.style.marginTop = margin +"px";
				else
					opt.style.marginLeft = margin +"px";

				if (margin < sl.max)
					sl.stopScrollUp();
			}
		,10);
	}

	this.stopScrollUp = function() {
		clearInterval(this.IdInterval);
	}

	this.startScrollDown = function() {
		var sl = this;
		
		this.IdInterval = setInterval(
			function() {
				var margin = sl.Str2Int(direcao == "vertical" ? opt.style.marginTop : opt.style.marginLeft);
				margin += 5;

				if(margin > 0)
					margin = 0;
				
				if (direcao == "vertical")
					opt.style.marginTop = margin +"px";
				else
					opt.style.marginLeft = margin +"px";

				if (margin > 0)
					sl.stopScrollUp();
			}
		,10);
	}

	this.stopScrollDown = function() {
		clearInterval(this.IdInterval);
	}

	this.Str2Int = function(str) {
		var negativo = str.indexOf("-") == 0;
		var num = parseInt(str.replace(/\D/g,""));
		if (!negativo)
			return num;
		else
			return -num;
	}

	this.max = -this.Str2Int(direcao == "vertical" ? opt.style.height : opt.style.width)+areaVisivel;
}