Sonic the Hedgehog 2 (ソニックザヘッジホッグ2, Sonikku za Hejjihoggu Tsū) is a platform video game developed by Sonic Team and Sega Technical Institute, and published by Sega. Originally released for the Sega Genesis in 1992, it was re-released for the Wii's Virtual Console on June 11, 2007 in North America, June 19, 2007 in Japan and on July 6, 2007 in Europe. The game was re-released on Xbox Live Arcade on September 12, 2007 and on iOS on April 20, 2010. The game introduces Sonic's friend, a fox named Miles "Tails" Prower, as a new playable character.

The story focuses on Sonic the Hedgehog and Tails, who must stop the series antagonist Doctor Ivo Robotnik from stealing the Chaos Emeralds to power the Death Egg. Sonic and Tails must defeat Robotnik's army and free their friends.

The game has sold over 6 million copies, making it the second best selling game on the Sega Mega Drive/Genesis, behind only its predecessor (both of which were packaged with the Genesis at different points in its lifespan). The game was compatible with Sonic & Knuckles, which possessed a "lock-on" feature which allowed the player to play as Knuckles the Echidna.

Main game

Sonic the Hedgehog 2 is a platform game in which the player characters are the titular Sonic the Hedgehog and Tails. The game's premise of builds upon the basic set-up of the original Sonic the Hedgehog game. Again, Sonic's nemesis Doctor Robotnik is planning world domination with his army of animals he's placed into robots, and continues to seek the power of the seven Chaos Emeralds - this time, to construct his ultimate weapon, an armored space station known as the Death Egg. Sonic, having befriended and teamed up with Tails, must progress through the levels, collect the emeralds himself, and defeat Robotnik.

The game plays as a 2D sidescrolling platformer, with the player directing Sonic through levels and around obstacles within a time limit of 10 minutes. Along the way, rings are collected and enemies are defeated. Star posts serve as checkpoints, where if Sonic loses a life, he would return to one. When the player has collected at least 50 rings, star posts can be run past for an optional Special Stage. There are a total of eleven zones; the first seven zones have two acts each, while Metropolis, the eighth zone, has three acts, and the last three zones have one act each. At the end of the last act of most levels, Sonic must fight Dr. Robotnik.

At the game's start, the player can select to either play as Sonic, Tails or both. In the latter mode, players control Sonic while Tails runs along beside him. A second player can join in at any time and control Tails separately, but the screen always stays centered on Sonic, frequently leaving Tails off-screen.

Improvements over the original Sonic the Hedgehog include significantly larger levels, faster gameplay, and a new stunt called the "Super Dash Attack", or "Spin Dash". The move allows Sonic to curl in a ball and spin while staying stationary, eventually resulting in a speed boost.

If Sonic collects every Chaos Emerald in the game by completing all of the special stages, he is able to change into Super Sonic. Sonic changes into his Super Form when he has collected at least 50 rings and jumps into the air. At this point, he turns yellow and becomes invincible. However, he can still get killed by drowning, getting crushed, falling into a pit, or running out of time. Additionally, his speed, acceleration, and jump height are all increased as well. While in this state, one ring is lost per second. When the player has no rings remaining or reaches the end of the act, Sonic reverts to his normal state.

Special stages

In Sonic the Hedgehog 2, there are 7 special stages. When Sonic collects at least 50 rings, he can use a star post to warp him to a special stage.

Special Stages track Sonic from behind while he runs through a pseudo-3D half-pipe course, collecting rings and dodging bombs. A set amount of rings must be collected to pass through each of three checkpoints and in turn to obtain the emerald itself. If Sonic collides with a bomb, he loses 10 rings and is immobilized momentarily. The order of stages is fixed in rising difficulty, and Sonic cannot enter any stage without passing the previous one. After finishing, Sonic is transported back to the star post he used to enter the special stage. He has 0 rings and the stage conditions are reset.

Multiplayer

The game also has a competitive mode, where 2 players compete against each other to the finish line, as either Sonic or Tails, in a split-screen race through three of the regular single player levels; Emerald Hill, Casino Night, and Mystic Cave, and a special stage. After one player finishes one of the regular levels, the other player must finish the zone within 60 seconds, or the level is ended instantly. In the regular levels, players are ranked in five areas (score, time, rings held at the end of the level, total rings collected, and number of item boxes broken). The player with wins in the most number of categories, wins the level. In the Special Stage, players compete to obtain the most rings. The mode ends when all stages have been completed, or if a player loses all their lives, in which his/her opponent will instantly win. Sonic 2 is one of the few games which utilizes the 320x480 display mode of the VDP inside the Mega Drive, however the image looks squashed when displayed.

Connection to Sonic & Knuckles

Two years after the 1992 release of Sonic 2, Sonic & Knuckles was released in 1994. Sonic & Knuckles possessed a special, "lock-on" cartridge, in which the player would put the Sonic & Knuckles cartridge into the video console, and then plug a second game into the top of the Sonic & Knuckles cartridge. The result of this unlocks Knuckles the Echidna in Sonic the Hedgehog 2, a variation of Sonic 2 where the player instead plays as Knuckles the Echidna, a character that hadn't been introduced until 1994's Sonic the Hedgehog 3.

The game is largely identical to Sonic the Hedgehog 2, with the exception that gameplay is altered due to Knuckles having separate abilities from Sonic or Tails. Knuckles can glide and climb walls, which allows him to gain access to areas that had been otherwise hidden or unreachable. Conversely, he cannot jump as high, making some situations, such as certain boss fights, more difficult. However, in this version of the game, the two player mode has been removed. The special stages are the same, though the amount of rings needed to progress has been decreased, and the score made within the stage no longer resets.