Without discreet codes it it a little harder to do. I have a home / splash for my theater with a button that reads "initialize" which toggles projector power, shows a please wait page with the free filmstrip animation on my website for about 45 seconds, then jumps to the page for selecting sources and controlling them, receiver volume , lighting, climate etc...

That page has a "theater off" button with a popup to confirm you actually want to shut the entire room down. That macro toggles projector power, turns off lights after 2 minutes and jumps back to the splash / initialize page with the single button.

I just checked and popups cannot be used as a please wait page, but you can fake it to look like it is very easily.

I do have a button to jump directly to theater control from the splash page should the projector already be on or if I had to restart the app for any reason.