This is being made by some of the same people who made Brawl (minus Sakurai). It looks very similar to Brawl with some minor differences, but the gameplay looks pretty good and who doesn't love the turtles?
They weren't able to confirm that you could use the GameCube controller (but they hinted at it), and they also hinted at a strong and impressive online mode, though they couldn't go into the details of that either.
I doubt this will be as good as Brawl, but who knows-- it looks neat and I will definitely give it a shot. Worst case scenario is that we have another fighter that is less traditional and more similar to Smash.
