Sonic the Hedgehog Mega Drive

In an attempt to steal the six Chaos Emeralds and harness their power, the game's antagonist Dr. Ivo Robotnik ("Dr. Eggman" in the original Japanese release) has trapped the animal inhabitants of South Island in cybernetic shells and metal capsule prisons. The player controls the titular Sonic the Hedgehog, who aims to stop Robotnik's plans by freeing his animal friends and collecting the Chaos Emeralds himself.

The game is split up into zones, each of which is split into three acts. The player must navigate through each zone to progress. At the end of each zone's third act, the player confronts Dr. Robotnik, who pilots a vehicle, in a boss fight with a theme unique to that zone. After completing the sixth zone, the player continues directly to the Final Zone for the last encounter with Robotnik. The player is given a certain number of lives, which are lost when Sonic collides with hazardous enemies or objects, falls off-screen, or exceeds an act's ten-minute time limit. If all lives are lost at any point in the game, the "Game Over" screen will appear, at which point the player can return to the beginning of the act with three lives if the player obtains continues from Special Stages. The game plays as a 2D side-scrolling platformer. The gameplay centers around Sonic's ability to run at high speed through levels that include springs, slopes, high falls, and loop-the-loops. The levels are populated with hazards in the form of animals Dr. Robotnik has trapped inside mechanical bodies (named "badniks" in the Western game manuals). The player must also avoid rows of sharp spikes, bottomless pits, and other obstacles. Sonic's main means of attack is the Spin Attack, in which he curls into a ball and rotates rapidly, damaging enemies and certain obstacles upon collision. This can be performed by jumping in the air or by pressing down on the D-Pad while moving on the ground. Scattered around each level map are gold rings, a signature Sonic series item. Collecting 100 rings rewards the player with an extra life. Rings act as a layer of protection against hazards—if Sonic is holding at least one ring when he collides with an enemy or dangerous obstacle, he will survive, but the rings in his possession will be scattered. If he is hit without holding any rings, the player loses a life. Shields and temporary invincibility can also be collected to provide additional layers of protection, but certain hazards, such as drowning, being crushed, falling down a bottomless pit or running out of time, will cause Sonic to lose a life regardless of rings or other protection. Lamp posts that act as checkpoints allow Sonic to return to the most recently activated post when he loses a life. If a checkpoint is activated and a life is lost as a result of running out of time, the time at the checkpoint will reset to 0:00. When Sonic reaches the end of Act 1 or Act 2 of a zone while holding at least 50 rings, a large ring appears through which the player can jump to enter a Special Stage. In the Special Stages, Sonic is curled up in his Spin Attack animation, and bounces off the bumpers and walls of a 360° rotating maze. In these levels, the player may earn continues by collecting 50 rings, but the main aim is to obtain the Chaos Emerald at the end of the maze without colliding with any of the "goal blocks" that instantly end the level. If the player collects all the Chaos Emeralds and completes the game, the most optimal ending sequence is shown. However, if not every Chaos Emerald is collected, a screen shows Robotnik taunting the player.

Source: Wikipedia