In 1990, developers on the Sonic Team created a blue virtual hedgehog named Sonic. In 1991, Sega published Sonic Team's first video game, Sonic the Hedgehog, for a worldwide release on the Sega Mega Drive/Genesis console. This 2D side-scrolling platform game became the first in a long and extremely popular series that follows Sonic's adventures and challenges as he works to defeat Dr. Eggman�or Dr. Robotnik in the Western adaptations�who plans to take over the world with the power of six Chaos Emeralds. Single players act as Sonic and help release Dr. Eggman's prisoners as well as collect the six Emeralds before Eggman does. The game consists of seven zones which are each split into three smaller acts. Each zone features a final boss fight with Dr. Eggman before the player can ultimately move on. Each act also possesses a ten-minute time restriction which, if exceeded, causes the player to lose a life. Sonic begins with several lives in case this happens, or if the player gets hurt or falls off the platforms. Several aspects of this game became hallmarks of the Sonic series. First, Sonic's ability to run at high speed with level designs tailored for his velocity; springs and loop-the-loops created a fun and challenging way to navigate levels without slowing down. Second, Sonic's characteristic attack�known as Spin Attack�consisting of Sonic curling into a ball and spinning toward an obstacle at high speed, damaging the obstacle or enemy upon collision. Furthermore, rings placed throughout the levels became a trademark of the franchise. Sonic can collect rings to add health, protection from harm, and even extra lives, depending on the number of rings collected. If the player finishes an act with a minimum of 50 rings, a Special Stage portal appears, taking the player to an extra maze level where more rings and possibly a Chaos Emerald can be accumulated. Sonic the Hedgehog garnered positive critical reviews, especially on the game's clear and colorful graphics. Sonic claims the title of the best-selling Sega Genesis and Sonic franchise game with over 15 million copies sold. Perhaps most importantly, Sonic the Hedgehog also boosted the Sega Genesis's popularity in North America. Since Sonic the Hedgehog, Sega expanded the franchise to include more games in several other genres, a cartoon series, toys, and media such as anime, manga, and comic books. Sonic himself also became Sega's official mascot, making him a character recognized by gamers and non-gamers alike. Other characters introduced in later Sonic games such as the friendly Tails, villain-turned-ally Knuckles, and rival Shadow the Hedgehog are also easily recognizable from years of popularity and exposure in different medias.