How do you get more games on sonic mega collection

There are many ways. But, since I'm ahardcore player at Sonic, I don't know any specific ways to unlock them. I just played Sonic 1, 2, 3, and Sonic and Knuckles. Play nonstop on these games, and you'll unlock: 1. Knuckles in Sonic 2 2. Sonic 3 and Knuckles 3. Blue Sphere 4. I'm not sure, but maybe Knuckles in Sonic 1 Hope this helps all Sonic fans!