3D Sonic, Make th story on par with Unleashed, The gameplay crossed with Sonic Adventure 1 & Generations, Tails & Knuckles are playable & Shadow is unlockable bonus. (No Wisps or Zeti.) 2D Sonic: Make it sprite based. (2.5D is to floaty. Sonic 4 episode 1 for example) Tails, Knuckle, Amy & Cream are all playable. Have more original levels mixed with nostalgia. Basically, Make Sonic Advance 4