Included as a double feature with Super Mario 3D World on Switch. Was described to me as an open-world Mario game, and I decided to give it a shot in June 2021 after listening to a Watch Out For Fireballs episode on SM3DW that talked about it a bit.
In practice it's a lot like a Mario Odyssey level, but fairly large and themed more in a “classic Mario” style. The world is a set of islands where each island has five goals following a fairly standard pattern, along with a bunch of one-off goals. There are a total of 100 goals but you can roll credits at about 50. Giant Bowser shows up occasionally to be scary, and later as a utility to destroy certain blocks and complete goals.
My least favorite goal is finding the calico kittens. I did most of them at the very end of the game when I was impatient to be done and didn't want to scour familiar levels again, so I cheated and went to a walkthrough. Also made worse since the kittens were mostly not in the world until I started the goal, so I wouldn't have stumbled across them early on.
The final boss cribs heavily from 3D Sonic: A high speed chase with lots of obstacles. It would be a bit too tough except you can spam the powerups you've been hoarding the whole game.
Overall elegantly constructed and a good time - just a few hours to play through, which is perfect, it would probably wear out its welcome if it was any longer. A bit more waiting around than I'd like, especially in the endgame: Sometimes Bowser shows up and the right thing to do is just wait him out. Also feel like they are testing out some tech here - it's got the “whole world active at once” feel of the last boss from breath of the wild that I assume they will double down on in the sequel, which throughly hides their clever streaming and rewards the mental map you've built. I wonder what a Metroid built in this engine would feel like, with more gating. Metroid is conventionally tunnel-heavy, so they'd have to solve indoor camera, but that's also a design device and maybe they can move past it.