Alex Kidd in Shinobi World

Alex Kidd in Shinobi World is a side-scrolling action game produced by Sega that was originally released for the Master System in 1990 and later re-released for the Wii Virtual Console in 2009. Although developed in Japan, it was released exclusively for the overseas market (North America, Europe and Brazil). The game stars Alex Kidd in a parody version of Sega's ninja-themed action game Shinobi, where Alex Kidd fights against caricatures of many of the enemies from Shinobi. It is the final video game to star the Alex Kidd character.

Despite being part of the Alex Kidd series, the game mechanics of Shinobi World are different from Alex Kidd in Miracle World and are much closer to the Master System version of Shinobi. Alex Kidd's basic attack is a sword slice, which can be used not only to destroy enemies, but also to open treasure chests. Inside such chests, the player can obtain items such as more health, throwing darts, a powered-up sword, extra lives, and a magic ball that will temporarily turn Alex Kidd into an invincible tornado. The throwing darts and powered-up sword will both replace the Alex's default sword until the player completes the stage or defeats a boss. Other actions that Alex Kidd can perform include a wall-to-wall jump and the ability to turn into a flying fireball after spinning around a street post, a rope or a horizontal bar.

Alex starts off each round with three hit points, but can fill out his health gauge to a maximum of six hit points. When the player has full health, all the treasure chests carrying hearts will carry extra lives in their place. When the player defeats a boss with full health, he will gain a 'Perfect Bonus' after completing the round. There's also a 'Secret Bonus' if the player completes an entire round without getting hit or losing life at any point.

An evil being known as Hanzo the Dark Ninja escapes after 10,000 years of confinement and kidnaps Alex Kidd's new girlfriend from planet Shinobi. After the kidnapping, Alex encounters the ghost of the ancient warrior who originally vanquished the Dark Ninja, who explains that the Dark Ninja intends to sacrifice Alex's girlfriend to conquer the world. The spirit of the ancient warrior fuses itself with Alex's body, lending Alex his strength, skills, and courage.

The game is composed of four different rounds roughly based on the missions from the original Shinobi, which are divided into three stages. The third stage is each round is a boss battle. The rounds are as follows.

Round 1 - Set in a city. The boss is 'Kabuto' (a parody of Ken-oh), a warrior in samurai armor who spits fireball and shrinks into a smaller size after sustaining damage.
Round 2 - Set in a harbor. The boss is a fleet of tiny helicopters spitted by a robotic face (a parody of both, the Black Turtle attack chopper and the Mandara Master).
Round 3 - Set in a bamboo garden. The boss is 'Robster' (a parody of the Lobster), who is an actual lobster.
Round 4 - Set in a mansion. The boss is Hanzo, who fights using several attack patterns similar to the Masked Ninja in the original Shinobi.