Today's Smash shot puts Mario in some sort of new locale that doesn't seem to be instantly recognizable from any Nintendo franchise. Sakurai shared these words with the reveal of this screenshot: "To be clear, the new Super Smash Bros. games do not feature a story mode like The Subspace Emissary."
This is probably then an adventure mode or evolution of the mode with focus on traversing simple stages opposed to something more full featured, which is fine by me. The stage seen above gives off a vibe as seen in the sequence below, which is taken out of the first trailer we got.
What would you like to see in the game in terms of single player modes?