window.addEvent('domready',function() {
    var nav=$$('div.navigation div a');
    for (var i=0;i<nav.length;i++) {
        nav[i].addEvent('click',function(e){
            var div=$('nav_'+this.get('id').replace('link_',''));
            if (this.hasClass('empty') && div) {
                var this_level=parseInt(div.get('class').replace(' hidden','').replace('level',''));
                var parent_level=this_level-1;
                var next_level=this_level+1;

                if ($$('div.navigation div.level'+parent_level+' a.active')) {
                    $$('div.navigation div.level'+parent_level+' a.active').addClass('empty');
                    $$('div.navigation div.level'+parent_level+' a.active').removeClass('active');
                }
                
                if ($$('div.navigation div.level'+this_level)) $$('div.navigation div.level'+this_level).setStyle('display','none');
                if ($$('div.navigation div.level'+next_level)) $$('div.navigation div.level'+next_level).setStyle('display','none');
                
                this.addClass('active');
                div.setStyle('display','block');
                return false;
            }
        });
    }
});