Sonic the Hedgehog 2 is a platform video game developed by Sonic Team and Sega Technical Institute, and published by Sega. The game is an installment in the Sonic the Hedgehog series, and focuses on the protagonist Sonic the Hedgehog and his friend, a fox named Miles 'Tails' Prower, who must stop the series antagonist Dr. Ivo Robotnik from stealing the Chaos Emeralds to power his Death Egg space station.
Originally released for the Sega Genesis/Mega Drive in 1992, the game was a critical and commercial success, with critics praising it for building upon the original Sonic the Hedgehog game. The game has sold over 6 million copies, making it the second-best-selling game on the console, behind only its predecessor in the Sonic series. Since its initial release, the game has been released in several compilations and download releases for various platforms, which were also generally positively received.
Sonic the Hedgehog 2 is a platform game in which the player characters are the titular Sonic the Hedgehog and Miles 'Tails' Prower. The game's premise builds upon the basic set-up of the original Sonic the Hedgehog game. Sonic's nemesis Dr. Ivo 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. The goal of the game is to collect the seven Emeralds from 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. A life is lost when Sonic is attacked by an enemy without rings, falls off-screen or exceeds the act's ten-minute limit. If all lives are lost, the 'Game Over' screen will appear. 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, the player must fight and defeat 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. 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. This also unlocks a different ending that shows Super Sonic flying by the Tornado, whereas not getting the emeralds leads to an ending with Sonic in his normal state riding on the Tornado.