var ap_ib = 0;
var ap_ia = 0;
var ap_hst = 0;

var offset = 195;

$(document).ready(function(){
	$('.shift-left').click(function(){
		target = $(this).children('var').text();
		var cpt = $('#' + target).css('top');
		var cp = cpt.substr(0, cpt.length - 2) * 1;
		np = 0;
		incr = true;
		if( cp < 0 ){
			np = cp + offset;
			incr = false;
		}
		$('#' + target).animate({top: np + 'px'}, 1000);
		if( target == 'ista-biblio' && incr ) ap_ib--;
		if( target == 'isti-autor' && incr ) ap_ia--;
		if( target == 'hist' && incr ) ap_hst--;
	});

	$('.shift-right').click(function(){
		target = $(this).children('var').text();
		var cpt = $('#' + target).css('top');
		var cp = cpt.substr(0, cpt.length - 2) * 1;
		num = $('#' + target + ' li.item').size();
		np = cp - offset;
		incr = true;
		if( num < 3 ){
			np = cp;
			incr = false;
		}
		$('#' + target).animate({top: np + 'px'}, 1000);
		if( target == 'ista-biblio' && incr ) ap_ib++;
		if( target == 'isti-autor' && incr ) ap_ia++;
		if( target == 'hist' && incr ) ap_hst++;
	});
});