then, maybe the simplies way to do is add in constants.php something like:
// set to 1 for under construction mode
define('CONSTRUCTION', 0);
then in "main" templates just before
include(ROOT_PATH.'includes/page_header.php');
add something like this:
if (CONSTRUCTION && $user_info['user_level'] != ADMIN) {
header("Location: construction.html");
exit;
}
it will redirect to construction.html page (located in root of 4images) if user is not admin.