Ninja Gaiden is a side-scrolling action-adventure game developed and published by Tecmo. The first game in the series was released in 1989 for various Nintendo platforms. It follows the story of Ryu Hayabusa, a ninja who must fight against an evil organization known as the Black Spider Organization.

Gameplay involves platforming, combat, and exploration. Players control Ryu as he fights his way through hordes of enemies to rescue his pet tiger, Kyū. The game features a variety of weapons, including swords, throwing stars, and smoke bombs. It also has a number of power-ups that can be collected throughout the levels.

The game received positive reviews upon its release, with praise for its challenging gameplay and atmospheric soundtrack. However, it was criticized for its difficulty level, particularly in the first world.

One notable aspect of Ninja Gaiden is its connection to the Street Fighter II series. Ryu Hayabusa is a character who appeared as a bonus fighter in Super Street Fighter II: The New Challengers.

A sequel to the original game was released in 1990 for various Nintendo platforms, titled Ninja Gaiden II: The Dark Sword of Chaos. It follows Ryu's journey as he seeks revenge against his nemesis, Mondo.

Ninja Gaiden has been re-released on several occasions over the years, including a 2004 remake for the Xbox and PlayStation 2 consoles. This version updated the graphics and gameplay while retaining the original's challenging spirit.

In recent years, a new Ninja Gaiden game was released in 2013 for the Xbox 360 and PC, titled Ninja Gaiden 3: Razor's Edge. However, this game received mixed reviews from critics, with many feeling that it deviated too far from the original formula.

The series has also inspired several spin-off games, including Ninja Gaiden: Shadow of Ryu and Ninja Gaiden: Dragon Sword for the Nintendo DS.

Overall, Ninja Gaiden is a classic side-scrolling action-adventure game that has endured through the years due to its challenging gameplay and atmospheric soundtrack. While it may not be as widely known today as some other classic games, it remains a beloved title among retro gaming enthusiasts.