"Sonic Blast is a video game in the Sonic the Hedgehog series developed by Aspect and published by Sega for the Sega Game Gear. It is known as G Sonic in Japan. It was released in December 1996 for both North American and European markets. A Japanese release followed later that year on December 13, being the last commercial title released for the system.
The game was also ported to the Sega Master System in Brazil by TecToy and released in December 1997.
Sonic Blast was later compiled with other Sonic titles in Sonic Adventure DX and Sonic Mega Collection Plus, and a demo of its ending can be unlocked in Sonic Gems Collection.
While this game was released at the end of 1996 in conjunction with the similarly named Sonic 3D Blast, the games have little in common. No enemies, levels, or bosses are shared between them. The story is also completely different; Sonic and Knuckles join together to collect five of the Chaos Emeralds and confront Eggman at Silver Castle."
"Unlike its pseudo-3D counterpart, Sonic Blast for Game Gear was a side-scrolling run and jump platform game. It was the last new Sonic the Hedgehog game released for the Sega handheld, and sported some of the most advanced features of the 8-bit series (although it was not very well received).
The two playable characters in the game are Sonic the Hedgehog and Knuckles the Echidna. The object of the game is to collect five Chaos Emeralds, in stages visually similar to the Sonic the Hedgehog 3 special stages, but instead require Sonic and Knuckles to collect rings as in Sonic the Hedgehog 2's special stages. Emeralds can only be obtained in the second act of each level. Finishing a special stage in the first act will gain the player an extra life instead. Similar to Sonic 3, special stages are entered through large rings hidden in the regular stages.
Much like Sonic Triple Trouble, when the player is hit by an enemy, he only loses some of his rings as opposed to all of them (in this game, 10 rings per hit). Sonic's maneuvers are similar to those in other games, but he has a special double-jump ability that allows him to reach greater heights, like with the electric shield in Sonic 3. Knuckles's abilities are his standard climbing and gliding, as seen in Sonic and Knuckles."
Source: Wikipedia, "Sonic Blast", available under the CC-BY-SA License.