Android Navigating Windows - Appcelerator Titanium

app.js

var mainWin = Ti.UI.createWindow({
    backgroundColor: "blue"
});
var btn = Ti.UI.createButton({
    title: "Click",
    width: 200,
    height: 50,
    backgroundColor: "#fff",
    color: "#000"
});
btn.addEventListener("click", function() {
    var win = Ti.UI.createWindow({
        backgroundColor: "red",
        modal: true,
    });
    win.open({
        activityEnterAnimation: Ti.Android.R.anim.slide_in_left,
    });
});
mainWin.add(btn);
mainWin.open();