Holy crap dudes, this game's art, sound, and UI is incredible. First off, let me say that the queues they're taking from the Mario Paint UI are super cool. The rocket ship deletes everything, the Undodog button is there. Smart callbacks, which makes sense since this is a 30th anniversary game. The design of the UI is great too, all the windows are crisp and colorful and there's a ton of smart looking sharing choices, which is a big step for Nintendo.
But really, I just want to talk to you guys about the sound design. See, when you place an item or block or enemy in the creation tool, it says the name of whatever you're placing. That'd already be kind of neat, but the kicker is that it's pitch shifted to match the music. This is such a smart choice that I might have actually died when I first realized what was going on while watching footage. It's so funny and esoteric and weird, and is exactly the type of small detail that makes me love Nintendo games. I'm super excited for this!
Check out the sound stuff in these videos, it will blow your fucking mind: