For a variety of reasons, including a dearth of relevant games just as the franchise was hitting its stride, Sonic fandom has developed a life of its own, and a rich history of fan-made games. A new entry is Sonic: Project Hero, which is an impressive-looking 3D game built in Unity that feels a bit like a better version of Sonic Adventure.
Fan developer Hero has been working on Sonic: Project Hero, and in honor of this year's Sonic Amateur Games Expo (or SAGE to those in the know), he's put together a playable demo for Windows and Mac. There aren't any actual stages yet, just a big Sonic-style skatepark filled with obstacles, loop-de-loops, hills, rings, and enemies to butt-stomp.
Sonic: Project Hero feels fluid and smooth, and the animations all look terrific. Hitting the right bumper gives you that little bit of extra spin to pick up speed, but Sonic will naturally get faster and faster the longer you run uninterrupted. You're also able to play as Tails and Knuckles in the demo (although I haven't worked out how to do that just yet). The camera can be a bit wonky, but I found that improved when I opened the options menu and inverted its Y-axis control.
The natural concern for a project like this is for the license holder to swoop in and promptly have their lawyers send out scary-sounding cease and desist letters, shutting down development. Fortunately, Sega has historically taken a much more lenient stance with Sonic, and in the case of 2017's Sonic Mania—a game Andy Kelly called "the best Sonic game in years"—even hired a team of developers drawn from the fan game and ROM hacking community to build their game.
Whether or not that's the end goal for Hero, Sonic: Project Hero is a promising and professional-feeling proof of concept that will be worth keeping an eye on. You can find it over at the Sonic Fan Game HQ.