Rain is the best hands down (makes me think a snow version, a storm version, I think weather is s good theme with more movement). It's the slickest & coolest. Space is next. Ideally, I would like a rotation system where the player can pick what backgrounds (as few or as many) they want to cycle. That way I can always pick my favorites to cycle & Chang my mind over time. Up to the player.
How did you guess?! The 10x combo is doable on Adept, but I am stuck on the next level as I can't get more than 85 seconds into a Fury game.
What do you think of a zen mode that's endless as long as you don't lose, I would enjoy that for late night playing