var nav_home = new Image();
var nav_home_over = new Image();
var nav_inventory = new Image();
var nav_inventory_over = new Image();
var nav_directions = new Image();
var nav_directions_over = new Image();
var nav_resources = new Image();
var nav_resources_over = new Image();

nav_home.src = 'resources/images/nav_home.gif';
nav_home_over.src = 'resources/images/nav_home_over.gif';
nav_inventory.src = 'resources/images/nav_inventory.gif';
nav_inventory_over.src = 'resources/images/nav_inventory_over.gif';
nav_directions.src = 'resources/images/nav_directions.gif';
nav_directions_over.src = 'resources/images/nav_directions_over.gif';
nav_resources.src = 'resources/images/nav_resources.gif';
nav_resources_over.src = 'resources/images/nav_resources_over.gif';

function beginRollover(obj) {
	document.getElementById(obj.id).src = eval('nav_' + obj.id + '_over.src');
}

function endRollover(obj) {
	document.getElementById(obj.id).src = eval('nav_' + obj.id + '.src');
}