hollow = new Image ();
hollow.src = "icons/hollow.gif";
red = new Image ();
red.src = "icons/red.gif";
brown = new Image ();
brown.src = "icons/brown.gif";
yellow = new Image ();
yellow.src = "icons/yellow.gif";
olive = new Image ();
olive.src = "icons/olive.gif";
green = new Image ();
green.src = "icons/green.gif";
blue = new Image ();
blue.src = "icons/blue.gif";

function swap(id, pic) {
  i = eval("window.document.images." + id);
  i.src = eval(pic + ".src");
}