It's not simple, you have to convert all the XML BGAnim stuff to Lua, then change any metrics that need changing (likely all of them). There's also probably a ton more steps I'm forgetting but it's not as easy as anyone thinks.
I guarantee you 100% of SelectMusic is doable, and not too hard, either. It's two PaneDisplays (which are already in the default theme so it's easier to get what values you want to change) and some restructured/moved elements from the normal SelMusic.
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