Played about 2 hours over the course of a few days, beat the campaign on a bunch of different modes and difficulties.

I think if you handed me this game and told me "two gamedev auteurs collaborated on this" it would probably be, like, the easiest thing in the world to guess it was Sakurai and Mizuguchi, lol.

It's a very solid falling puzzle game, but it's also kinda clear why it didn't really go anywhere. My main issue is that it's built entirely with multiplayer in mind, with most of the singleplayer modes being you vs. the CPU. The problem here is that falling block multiplayer modes aren't really super satisfying, with you just needing to play roughly the same exact way regardless of what your opponent is doing. It's just an endurance until someone tops out, which tends to be short enough for the endurance to not really be satisfying in of itself.

Which, don't get me wrong, is fine, I've played a lot of 1v1 Tetris, so it's still fairly fun. But I was very much yearning for a marathon mode like in Lumines or Tetris Effect which brings you through all of the different levels in a sequence, rather than just an all-star mode-style campaign which throws you up against a random subset of opponents before the same final boss every time. There just isn't that sense of finality, but that's probably just not a goal for this in the first place--there's a very clear lineage between this and other Sakurai games like Kirby Air Ride and, of course, SSB in terms of its progression and unlock system. There's plenty of room for self-directed goals in here, if you're so driven.