If you are developing a Google Hangout App, don’t be surprised if you press the “Enter a hangout in developer sandbox” link and get an ugly 404 error.  Take the resulting URL, that looks like:

https://hangoutsapi.talkgadget.google.com/hangouts?authuser=0&gid=110709744297

grab the GID (in my case 110709744297), and form the URL:

https://plus.google.com/hangouts/_/?gid=110709744297

and now you’re back testing again.  (last night I had an update for AnywhereBoardGames, and was greeted by this nasty surprise).