Sonic the Hedgehog 2 (8-bit)

Sonic the Hedgehog 2 is a side-scrolling platform video game developed by Aspect and released by Sega for their Sega Master System and Game Gear formats. The Master System version was released in Europe on October 25, 1992, and in Brazil around the same time. The Game Gear version was released in Europe on October 29, 1992, in North America on November 17, 1992 and in Japan on November 21, 1992. Being released before the 16-bit version for the Mega Drive (Genesis), the 8-bit editions of Sonic the Hedgehog 2 represent the debut of character Miles "Tails" Prower, Sonic the Hedgehog's best friend who became a recurring character in the series.

Storyline
Sonic decides to come back home after a short errand, but is shocked to see the place almost deserted. On the floor is a note written by Tails, explaining that he and the animals of the island have been kidnapped by Dr. Robotnik, and that his own safe return is exchanged for six Chaos Emeralds, to be given to six robots. There was no time to waste! Immediately Sonic once again is out to thwart the evil scientist's plan for global domination!

(The storyline above comes from the game's instruction booklet. It is contradicted by an opening cinematic where Tails runs ahead of Sonic, and Sonic witnesses his kidnapping.)

Gameplay
Advances made in this game include Sonic's ability to grab back rings scattered when hit by an enemy as well as being able to smash through certain walls, capabilities not implemented in the 8-bit versions of the original title. Oddly enough, there appears to be no Spin Dash, though this may be because this game was released before the Genesis version, which introduced the Spin Dash. Uniquely, this game includes levels in which Sonic must ride a mine cart, and a hang glider, the latter under full player control and a reasonable simulation of physics. There is also a large bubble in underwater levels which raises Sonic upwards until he hits a ceiling, enemy or obstacle. Sonic is also able to skim across the surface of water.

There are seven zones in total, each comprising three acts. In the final act, that level's boss is faced, but without any rings to collect. Rather than facing Robotnik himself (with the exception of the final stage and some involvement in the first boss), Sonic faces up against a bunch of robotic animals, such as a sumo pig and a circus sea lion.

At the end of Acts 1 and 2 of each level, a panel is spun, with a reward given based on what it lands on:
 * Robotnik: No prize. This panel comes up most often in the game.
 * Ring: 10 rings added to final ring tally. Usually obtained by having a ring count that is a multiple of ten.
 * Sonic: Extra Life
 * Tails: Continue

Item boxes are largely the same as the first game (although the restart marker and shield devices have been removed), and as usual, Chaos Emeralds are scattered throughout the stages. Each is found in the second act in each of the first five zones. If the player collects these five and then destroys Mecha Sonic (called "Silver Sonic" in the English manual) in the sixth zone, the sixth is awarded and the player may access the final stage (Crystal Egg), in the third act of which Robotnik is faced in a climactic boss battle. Players able to complete the full task are rewarded with the game's "good ending"; for those who fail to collect all of the emeralds, play ends after Mecha Sonic's destruction with a more downbeat end sequence (in which Tails is assumed to be dead).

Although Tails is not a playable character, he appears in the title screen of every zone (which is shown in the beginning of each act in the zone), where he appears together with Sonic at a picture that describes how the zone looks.

Differences between versions
The Game Gear, with its lower screen resolution, naturally results in the Game Gear version having a smaller visible screen area than the Master System edition, causing many to consider the Game Gear version the more challenging title - when facing the boss of the Underground Zone, for example - the reduced screen area either side of Sonic gives the player less time to react to hazards moving onto the screen. Other bosses were also affected: the Green Hills Zone battle takes place in a smaller, steeper arena; the escape chute cannot be seen while fighting Robotnik in the final Crystal Egg stage.

The music for the intro sequence is also different, the Game Gear version using the Scrambled Egg music for the scene showing Robotnik escaping with the captive Tails, with the tune that was played in this prelude in the Master System version instead employed on the title screen. The hand-held edition also features dark blue (instead of green) water in the second Act of the Aqua Lake Zone, and omits the game's second "High Speed" item box, which may be found in the Master System version of this stage.

In addition, the two versions have different themes for boss battles, as well as for their endings (the Master System uses a somewhat sad sounding tune for both the bad and good endings, whereas the Game Gear has a separate more upbeat tune for the good ending). This is strange since the Master System version actually contains both of the ending music in the game's code, but only one of them is used. A rather interesting note was that the music for Green Hills Zone was featured as the theme song for the Japanese and European versions of Sonic CD, and a negative remix of the tune is used for Mecha Green Hill Zone in Sonic Chaos.

Later re-releases
The Game Gear version of Sonic the Hedgehog 2 is also included in the following compilations:
 * Sonic Adventure DX for the Nintendo GameCube and Windows PC
 * Sonic Gems Collection for the Nintendo GameCube and Sony PlayStation 2.