
After collecting the Chaos Emeralds from the Special Stages (which are similar to the originals but with new textures and music, not to mention much harder), they can transform into their Super forms that have special abilities never seen before in 2D Sonic games, such as flying or using special powers by the cost of rings. It has five playable characters (Sonic, Tails, Knuckles, Mighty and Shadow) which are very differentiated by their special abilities (Tails and Knuckles play similar to the original games, Sonic has a homing attack and peel-out, Mighty can use a insta-shield attack and is the only character that can use the special abilities of the shields, Shadow plays similar to Sonic but can double jump).
See the Wiki page for more info.Gameplay is the same as the original Sonic The Hedgehog, but, as of the latest versions, it has evolved to incorporate elements from more recent Sonic games.
Credits have been edited each character has a unique end pose on the ending sequence.
Elemental shields, ala S3K, have been added. There is also a separate save slot for a character’s original mode. “Original Mode” allows you to play the original levels from Sonic the Hedgehog, using all of the additions from Sonic Megamix (such as bug fixes, moves, preferences, etc). Cheat codes have been changed - figuring them out will grant you access to a new, special level select (which is a bit buggy - just don’t hit left/right on zone selections =P). There is now a “preferences” screen, where you can customize certain aspects of the game (suggestions are welcome). Most levels (not all) have a small intro, ala S3K, where they perform some sort of action when starting the level i.e, running in from the left.
Each character now has a unique set of moves (though Sonic and Shadow share the homing attack). All level layouts edited (some complete others pending).