So, I got curious as to what this might look like, and here's what I found: C=Classic, M=Modern, A=Avatar, T=Team. I organized each zone following a "classic, modern, avatar, team, boss" structure. GREEN HILL: C10: Faded Hills M1: Lost Valley A20: Guardian Rock T7: Arsenal Pyramid C11: BOSS - VS. Eggman CHEMICAL PLANT: C18: Chemical Flow M21: Network Terminal A2: Spaceport MYSTIC JUNGLE: C13 - Casino Forest M8 - Luminous Forest A14 - Aqua Road M9 - BOSS: VS. Infinite SUNSET CITY: C3 - Ghost Town M15 - Sunset Heights A12 - Park Avenue T19 - BOSS: VS. Metal Sonic (the level select doesn't designate this as a boss act, but that's basically all it is) METROPOLIS: M23 - Metropolitan Highway A16 - Capital City T24 - Null Space A17 - BOSS: VS. Infinite DEATH EGG: C22 - Death Prison M6 - Egg Gate A4 - Prison Hall M5 - BOSS: VS. Zavok EGGMAN EMPIRE FORTRESS: C28 - Iron Fortress M26 - Mortar Canyon A25 - Imperial Tower T29 - Final Judgment M27 - BOSS: VS. Infinite TRIO30: FINAL BOSS: VS. Death Egg Robot TOTALS: Classic: Six acts, one boss Modern: Seven acts, three bosses Avatar: Seven acts, one boss Modern + Avatar: Three acts, one boss Trio: One boss Notables: Chemical Plant is the only zone without a boss, but Eggman Empire Fortress has two. Classic Sonic never fights Infinite, and is the only character "missing" his own act within a zone in Metropolis. Overall, Classic Sonic is playable in only 26.6% of the levels, while Modern Sonic is in 50%, and the avatar is in 43.3%.