I figured out how to clear the game UI. (chat, menu, shop, game pad icon, skill bar) What could you use this for? I don't know.

1. Go into chat
2. Tap onto someone's name
3. Click add friend
4. Tap the (X) furthest to the top right before the friend confirmation box pops up
5. If you did it right when you click "ok" you should be met with a TWOM game with no buttons, chat box, or anything

You won't be able to do anything in this state, so you'll have to restart the app.