Thought I'd write down how the gameplay breaks up for the 3DS version for anyone curious. Spoilers and such.
Windy Hill:
- Tutorial level
- Act 1 is mainly 3D Galaxy-esque gameplay, pretty linear, some Asteroid wisp gameplay, ends in a giant Caterkiller chase.
- Act 2 is one long dark, linear 3D cavern, atmospheric music, a lot of chasms, and you can go back later and use Fireburst wisp.
- Act 3 is completely 2D, Green Hill Zone-esque with pleasant music, can go back later and use Laser.
- Boss is the purple guy chasing you around a globe with his giant moon ball, you can repeat later with use of Fireburst.
Desert Ruins:
- Act 1 is a big open 3D level, multiple routes, Asteroid gameplay, giant worms, pretty great level.
- Act 2 is 2D, inside a dark tomb, some switch puzzles. Can go back later with Drill and find secret routes.
- Act 3 is 3D, and one long multi-part obstacle course with sand that shoots you along, can go back later with Quake.
- Boss is the fat yellow guy, not too different from first boss. You can use Asteroid on him. I beat him in 45 seconds first go.
Tropical Coast:
- Act 1 is 2D, and almost entirely underwater, lots of Drill use and giant puffer fish, really pleasant music. Like Colours' Aquariam Park (not as good though).
- Act 2 is a giant juice blender! This is one of my favourite levels. You explore sub-levels to find giant apples needed to go into the main hub machine. The applejuice then carries you higher. You can use Lightning on this level but I haven't really found much of a use for it yet.
- Act 3 is one massive 3D Drill level. Drill does not work well in 3D. You explore huge multi-route levels, but the wisp controls like crap. There's a few parts where you drive it up the middle of a huge vortex. It's tricky and pretty bad.
- Boss is the old guy. You run around a globe in 2D, countering the fruit he rolls at you. Now and then you can use Drill to surprise him.
Frozen Factory:
Act 1 - Stodgy snowboarding section, introduced to the Lightning wisp which is used for platforming and chain-kills. You also roll a few snowballs around and finish with more snowboarding.
Act 2 - 2D level, lots of platforming and wall-dashing, and some opportunities for Laser when you get it later.
Act 3 - Massive 3D puzzle-heavy level. A giant bastard snowball follows you around for most of the level and you have to avoid it. Also lots of snowballs to push into holes, and some Quake wisp action you can replay it for.
Boss - The girl. She's in a giant snowman and you have to use Lightning to swing up high enough and get in a hit.
Silent Forest:
Act 1 - Quite a good 3D spherical level. You get Quake here, and spent a lot of time rolling around crushing Cluckoids and opening up paths using Quake-only switches. Also some 3D skydiving bits.
Act 2 - More 3D, this time on a linear path. Lots and lots and lots of grind rails, Cluckoids on grind rails and some optional use of Lightning.
Act 3 - 2D! Amazing music and lots of platforming, with some use of Laser. A giant owl keeps watch in the second part of the stage and changes the level design slightly if you get spotted.
Boss - Emo-kid. You have to identify which of the many owls he's in, and try not to hit the decoys, looking around using gyro. After a few hits he goes down.
Sky Road:
Act 1 - 2D level that plays as a homage to Casino Night Zone. You can play giant bingo, and yeah, it's not a bad platforming level really. Again, Laser has a use here.
Act 2 - Fucking terrible level. Decides to use Asteroid for pinpoint chasm platforming for nearly the entire duration. Would rather feed laxatives to seagulls and then go for a quick jaunt along the beach then play this again.
Act 3 - Another dud, although it has an exciting finish. You spend most of it using gyro to control Sonic on a rocket, although one-hit KO's. Luckily after a few deaths it'll give you the stealth bomber remote that makes the whole thing more bearable. A sprint along linear 3D levels at the end lets you blow off steam, and you can come back and use Fireburst if you like.
Boss - the main guy. You skydive in 2D whilst waiting for an opening on his big dragon thing. Occasionally you can cause more damage with Laser.
Lava Mountain:
Act 1 - You fight purple guy and fatso again. That's it.
Act 2 - You fight green girl and blue guy again.
Act 3 - You fight old guy and red guy again.
Boss - Final boss. Feels a bit like Colours' final boss, but worse.
Special Stages:
Collect coloured spheres in space! By spinning around on your computer chair like a retard. Not actually that bad, but the more difficult ones are murder. Also....don't do it on a full stomach, eh?