I bought this game because Marble Madness is a fond memory of my childhood, and similarly Super Monkey Ball is a big favorite of mine today. But I knew I was in for a treat when, within the first 2 minutes of booting up the game, I somehow got the "7 seconds of airtime" achievement for getting myself stuck between a rock and a wall in the hub world, having to restart. And then immediately after, somehow all the doors in the hub world got stuck shut and I had to restart the game. Again.
Beyond that, the official content is lacking and easy to breeze through within an hour. Maybe it's just my aforementioned love of games like Monkey Ball, but the game's difficulty seemed like a joke most of the way throughout. Instead, most of the challenge came from learning the game's sometimes nonsensical air controls and the overall general glitchy behavior, like occasionally randomly losing the ability to jump until you reset to the last checkpoint. (Speaking of checkpoints, when you warp back to the checkpoint, PLEASE point the camera in the direction you're supposed to go. I kept going the wrong way after recovering from a checkpoint.)
As for the level design, it feels uninspired with too much pointless empty space. Everything just kinda mushed together and nothing was particularly memorable. If it weren't for the change from one late 90's-looking texture pack to another, I wouldn't even be able to tell the levels apart. They're all just floating platforms over a generic backdrop. I would have liked to see more consistent use of stage gimmicks throughout each stage, because almost every level had one or two unique gimmicky sections (like the windy part at the beginning of the desert level) and then beyond that was just standard platforming. Use the wind effects in the desert more, use the snowballs in the snow level more, use the windmills in the sky ruin stage more, etc. Also, we get that you like your giant speedboost ramps into the finish line at the end of the level, but for god's sake come up with some variety on how you handle your big finales to each level. The final jump of the game just felt so utterly anticlimactic because the gimmick was way overplayed by then (although the no-frills ending credit sequence didn't help with that feeling either).
The hardest parts of the game (when it comes to level design), I found, were sections during which you had next to no control. For example, I had lots of issues with the big loop about halfway through the space level because there was just no way to really guide the ball safely through it, and if it decided to just roll off the side of the track, then welp, I was falling off and it was back to the last checkpoint for me, where I would have to spend another 30 seconds jumping on that elevator that never seemed to want to work.
Long story short, this game feels like a tech demo from the late 90's/early 00's. Most of the stuff here works, but just barely. There's some decent ideas, but it needs some more cohesion and polish before it's really worth it. As it is, it's a pretty boring experience where the most engaging part is feeling rage at the game's questionable physics and occasionally glitchy behavior. You're much better off sticking to games like Super Monkey Ball and Marble Blast in the mean time.