This is Carnival Nights Zone from Sonic 3!(Pardon the sloppiness, I'm not so good in Paint)
The four platforms are each starting platforms for the four players(this gives you a good example of the scale of the level). The top two are normal, stationary platforms. The bottom two are slanted, thus, if you land on certain points of them you will slide downward. You can jump through the top two platforms, but the bottom two are completely solid.
The two red and white things at the very bottom center are supposed to be those annoying barrels that you never figured out how to get past when you were seven playing Sonic 3. If you jump on them in Smash, they will bounce you upward at the height of a double jump. If you double jump them with the right timing, or if the barrel is jumped on multiple times in a certain time span, the barrel will fall and won't re-appear for a given amount of time. Thus, if both barrels are gone, and you slide off the bottom platforms, you will basically be plummeting to your death and will have trouble making it back to safe ground.(though it isn't impossible with any given character, it's just, if you try to recover you will just lnd on the platfiorm and slide again, making it quite a struggle!)
The middle platform? It spins clockwise at a slow pace, so you also have to be careful not to fall off! The farther away it is from a perfect 180 degree line, the more you slide. So don't get too caught up in battle, because this is anarea where you must be constantly moving. Don't worry if you fall off, though, because you can jump through the platform itself if you react fast enough.
Oh, I almost forgot to mention the white and red orbs to the left and right of the center platform. Remember the floating bumper in the original Peach's Castle from SSB64? Well, these act sort of like that one did, except they don't move. They're basically mid-air bumpers, I should say. Except they're classic Sonic style, and they make make the little 'boop' sound when you hit them like in the original Carnival Nights(Or are they from a different zone...?)
I'm begining to sound a little like Sakurai here. =P