Sonic 2 Modern Neon & Classic Neon is a ROM hack likely presenting two distinct visual styles within the same game. 'Modern Neon' probably indicates bright, modern-looking visuals, while 'Classic Neon' might utilize a neon aesthetic to recreate the look of the original game.  This hack seems to focus on contrasting graphical styles in a single ROM, remaining outside of official Sega development.

Sonic 2 Modern Neon & Classic Neon

Sonic 2 Master Edition 3 spaces.ru 