$(function() {

	$(".btn")
		.mouseover(function () {
			this.src = this.src.replace(/^(.+)(.png)$/, "$1_over$2");
		})
		.mouseout(function () {
			this.src = this.src.replace(/^(.+)_over(.png)$/, "$1$2");
		})
		.each(function () {
			this.preloaded = new Image;
			this.preloaded.src = this.src.replace(/^(.+)(.png)$/, "$1_over$2");
	});

	$('.mainBtn').click( function() {
		showMenuPanel( $(this).attr('id') );
	});
	
    

});

var menuId = '';

function showMenuPanel( _menuId ) {
	
	if (menuId != _menuId) {
		
		if (menuId != '') {
			$('#'+menuId+'_panel').slideUp();
		}
		
		$('#'+_menuId+'_panel').slideDown();
		
		menuId = _menuId;
	}
}