// Deck layer switching
// Use with example 3-17

var deck = document.getElementById("fly-deck");
var selected = deck.getAttribute("selectedIndex");
if (!selected)
    selected = 0;
if (selected < 2)  {
    selected = parseInt(selected) + 1;
    deck.setAttribute("selectedIndex", selected);
}
else  {
    selected = 0;
    deck.setAttribute("selectedIndex", selected);
}