Yoshi's Island is a 2D side-scrolling platform game.[2][3] Its story begins as Kamek, a Magikoopa[4] in care of young Bowser, attacks a stork delivering baby brothers Mario and Luigi. They succeed in kidnapping Baby Luigi, but Baby Mario falls out of the sky and onto the back of Yoshi,[3] the friendly dinosaur.[5] The player controls one of many Yoshis, which take turns traveling through 48 levels across six worlds[6] to rescue Baby Luigi and reunite the brothers.[3] In the Super Mario series platform game tradition, the player controls Yoshi with a two-button run and jump control scheme. The player navigates between platforms and atop some foes en route to the end of the increasingly difficult levels. Yoshi also collects coins to earn extra lives[7] and retains his long tongue from Super Mario World.[2] The game centers more on "puzzle-solving and item-collecting" than other platformers,[5] with hidden flowers and red coins to find.[6] Levels include mines, ski jumps, and "the requisite fiery dungeons".[8] Every fourth level (two in each world[6]) is a boss fight against a large version of a previous foe.[5]
In a style new to the series,[8] the game has a coloring book aesthetic with "scribbled crayon" backgrounds, and Yoshi vocalizes with its every action.[6] Expanding on his "trademark tongue" ability to swallow enemies,[4] Yoshi, as the focus of the game, was given a new move set: the ability to "flutter jump", throw eggs, and transform. The flutter jump gives Yoshi a secondary boost when the player holds the jump button.[3] It became his new "trademark move", similar to that of Luigi in Super Mario Bros. 2. Yoshi can also pound the ground from mid-air to bury objects or break through soft earth, and use his long tongue to grab enemies at a distance.[7] Swallowed enemies can be spat as projectiles immediately or stored for later use as an egg.[3] The player individually aims and fires the eggs at obstacles via a new targeting system. The eggs also bounce off of surfaces in the environment. Up to six eggs can be stored this way, and will trail behind the character.[2] Yoshi can also eat certain items for power-up abilities. For instance, watermelons let Yoshi shoot seeds from his mouth like a machine gun, and fire enemies turn his mouth into a flamethrower. Other power-ups transform Yoshi into vehicles including cars, drills, helicopters, and submarines. A star power-up makes Baby Mario invulnerable and extra fast.[7]
While Yoshi is "virtually invincible", if hit by an enemy, Baby Mario will float off his back in a bubble while a timer counts down to zero. When the timer expires, Koopas arrive to take Baby Mario[3] and Yoshi loses a life.[9] The player can replenish the timer by collecting small stars[3] and power-ups.[5] However, Yoshi can also lose a life instantly if he comes into contact with obstacles such as pits, spikes, lava, and thorns. Similar to Super Mario World, the player can hold a power-up in reserve, such as a "+10 star" (which adds ten seconds to the Baby Mario timer) or a "magnifying glass" (which reveals all hidden red coins in a level).[6] These power-ups are acquired in several minigames.[6] At the end of each level, the Yoshi relays Baby Mario to the successive Yoshi.[3] If the player perfects all eight levels in each world by finishing with all flowers, red coins, and full 30 seconds on the timer, two hidden levels will unlock.[7] There are three save slots on the cartridge.[3]
The Game Boy Advance version adds an exclusive bonus level for each world with 100% level completion.[6] It also includes four-player support via link cable,[3] but only to play Mario Bros., a pack-in feature also included on the other Super Mario Advance games.
