Sonic the Hedgehog Genesis is a GBA port of Sonic the Hedgehog, originally released for the Sega Genesis. It was released in November 2006, to celebrate the franchise's (and the original game's) 15th anniversary. There are several differences from the original game.
- The screen ratio has been reduced to fit the GBA screen and keep everything the same size.
- Sonic's "death" animation is only shown for a split second. Whenever the player loses a life, the drown animation is shown instead.
- A new Anniversary mode has been added where the player can use the spin dash, which was introduced in Sonic the Hedgehog 2, although there is an original mode that could be played without this feature.
- The music and some sound effects were remade.
- The gameplay and music are constantly out-of-sync, as seen in the credits medley.
- The game lags more than the original and is riddled with glitches. This is because the game uses Sonic Advance's game engine. Sonic Advance had smaller sprites, so the bigger sprites of Sonic 1 is partially why the game lags. Coupled with the small screen, this caused a lot of negative reviews.
- The debug mode and level select mode has been removed, but an unlockable juke box room has been added.
- The game saves any zones/acts completed so that they can be replayed or continued, but does not save any Chaos Emeralds or the player's score.
- If the game is quit without getting a game over, retry can be selected at the mode select screen so the player can continue the game with any emeralds and score, and will start on the act where the player left off.
- Some bosses, like the Eggmobile (mine dropper) in Starlight Zone, can be damaged by jumping and hitting them, which wasn't possible in the original version.
The goal of the game is to get to the end of the act and flip the flag while collecting rings, stomping enemies, and freeing little animals. At the end of every third act is a boss fight between Sonic and the evil Dr. Robotnik, after which you open a capsule containing little animals.
Sonic the Hedgehog Genesis consists of seven zones. Each zone consists of three acts. The zones are as follows:
- Green Hill Zone
- Marble Zone
- Spring Yard Zone
- Labyrinth Zone
- Star Light Zone
- Scrap Brain Zone
- Final Zone
After collecting at least fifty rings and completing the first or second act, there will be a giant ring that takes you to a Special Zone if the player jumps through it. In the Special Zone, the player has a chance to collect one of six Chaos Emeralds. The Special Zones consist 2-D mazes that rotate costantly. The goal is to find the Chaos Emerald at the end without touching the goal orbs that take the player out of Zone. The player also has a chance to collect a lot of rings for 1-ups or to improve his/her score.
The reception was negative, as many reviewers criticized the game for its slow frame rate, music, and glitches. Most called the game "unplayable."