Probably the best 2D Mario game I'd played in a very long time. Highly imaginative and with enough challenge to keep engagement, it's a game that feels too short though not for a lack of content - It's something you just want to keep going.
On the topic of new concepts, I really enjoyed the Souls-esque ghost system where you can see players navigating stages in real time - Players who you can help should they meet a premature end, or should you struggle with a puzzle as was the case of myself and two Toads being helped by a hyperactive Toadette.
My one complaint is the lack of a post-game world that really challenges a player's collective experience, as the special world is itself woefully short.