I can understand people not being too impressed with Green Hill Zone, but Studiopolis Zone looks amazing and is 99% new art assets. If anyone can point out a Sonic fan game as visually accomplished as Studiopolis Zone, I'd love to see it. Moving on from that, I have to admit that I miss the Red Star Rings. Hunting them down added a lot of replay value to Sonic Colours and Sonic Generations (as did the Star Coins in the New Super Mario Bros series). Maybe Sonic Mania could keep track of how many giant rings you've found in each Act?