With Sonic R mode, you can actually play as all characters instead of Sonic. I disabled thoking, so the only character that actually gets a burst of speed forward would be Knuckles' gliding. Sadly, 4 characters out of soon-to-be 11 characters are double jumpers. Those being Sonic, Amy, Jet, and Shadow. I was thinking of giving only Sonic the shield movements he had in Sonic 3 & Knuckles, but that's not on the top of the to-do list. The last level + Cream and Rouge needs to be finished first.
I also keep forgetting to make shields hurt you in Races. There has always been absolutely no point in adding them in race stages (mostly the black shield). If they could be used to hurt other players, it would make racing similar to Mario Kart.
I could also tell you all the new mind-bending stuff that I've added, like Knuckles' new gliding extra, but the mod is close to being released. It's best if you just wait. Something minor would be that I added Amy's Birdie from Sonic Adventure. As far as I know, there are only 3 puffballs that float around Sonic characters. Birdie, Cheese, and Chip.
Semi-minor is a long but awesome level I made for Sonic R. It took days to complete, and getting all 3 laps may take up close to 4:30 minutes, but it has 2 3D areas and 2 2D ones, and 3 new features that makes the level more fun to play. I stopped working with scenery halfway through the level so that I could finish the level, so finishing that could take a while.
Speaking of 3D to 2D, I did fixed it up. Stepping onto the 3D to 2D sector will automatically force you to stick to the designated Y position with your viewing angle to either East or West. It took me a while for the Y-position one, that I ended up with tagging the sector to a linedef. That linedef's lenght determines your Y position. So if your sector is far away from the middle of the level, that linedef will be pretty long. For it to work in the bottom of the level, the NOCLIMB flag needs to be turned on so that the linedef lenght will have a negative value. Instead of 1024, it's -1024. I have already tested this on laggy servers running at fast speeds, and it seems to always work. So now there's no need to use Speed Pads to reposition you in the wrong spots.