I've watched gameplay of all available levels available and wow -- game looks absolutely amazing.
Boss battleBoss hasn't even appeared and we're at the entrance, but i'm already floored by the visuals of the arena.
Bell powerup that you need to beat the boss is placed at the entrance, but you don't even need it, cause the boss himself will provide if you will miss it.
Rounded arena reminds of Poltergeist boss from Galaxy or Bowser Jr. giant robot fight where you also needed specific power up to beat him.
Classic Nintendo cue to mark boss' weak spot with a bandaid.
Mice HillsThis is the only shown level that is actually rehashing SML3D Land gameplay style. Every other levels have other distinctive gimmicks to make them different.
Even then big sprawling open area in the beginning reminds me or Mario 64 rather than SML 3D Land. One notable introductions is rolling parts of the landscape from NSMB series. Dungeon in the middle is vanilla SML 3D Land-style diorama. Even there, hidden area with a green star is pretty interesting.
Glass tubes levelThis level reminds me of NSMB Wii/U levels where you had separated floating islands in the mountains with those black thingies going by predetermined route between them, you had to jump from island to island all the while avoiding or destroying them. They just took this game play, transformed islands to 3d areas and made black thingies go horizontally inside the tubes.
Spinning jumps! It looks like jumping on your co-op partner's head makes you spin. I wonder if you can do it by yourself from the ground like in Sunshine.
Star power up that are given thoughout entire level also remind more of 2d Marios. Also Peach changes her dress a bit after taking fire powerup and blue Toad just becomes red Toad.
Nice part with five keys in the tube.
Level 6-3This level is designed around cat power up, and has a lot of alternative routes and vertically oriented gameplay, closer to Sunshine levels than to 3d Land or 2d series.
Camera in co-op is a problem though. I can see constantly getting off the screen becoming a nuisance in such complex 3d level like this. Maybe the can do dynamic splitscreen or tone down complexity of the 3d environment, make it more open so that camera can see everyone at all times, i dunno.
Level 1-5I don't think i understand how this works in co-op. Should everyone press jump button at the same time to do special jump? Can other players who weren't on the "driver's seat" compete with Toad who took all points simply because he was the first?
Otherwise it looks like one of the ride levels from Galaxy games.