Ninja Gaiden (also known as Ninja Ryukenden and Shadow Warriors, in Japan and Europe respectively) for the arcade is a completely different game from the well-known NES action game of the same name. Originally released for the arcade in 1988, it was later released for the Atari Lynx, PC, Amstrad CPC, Commodore 64, Amiga, and ZX Spectrum. Developed and published by Tecmo, Ninja Gaiden is a traditional beat-em-up similar to other beat-em-ups of the time such as Double Dragon or Streets of Rage. Ninja Gaiden was also included as an unlockable in the 2004 Xbox game, Ninja Gaiden.
There are only a few differences between the three versions of Ninja Gaiden. While Ninja Gaiden and Shadow Warriors (the European version) are identical, Ninja Ryukenden differs in a few minor ways. There are many differences in music between the versions, but the only track that is completely different is one that is played during the Grand Canyon level. In addition, enemies in Ninja Gaiden need to hit the player much less to do damage, while in Ninja Ryukenden enemies must preform multiple hit combos to do damage. In Ninja Ryukenden, a voice can be heard saying Ninja Ryukenden at the end of the game, while nothing can be heard in Ninja Gaiden.
Taking place in the United States, Ninja Gaiden follows an unnamed ninja protagonist who is traveling through various locations across the United States, fighting a descendant of Nostradamus who leads a cult.
As a traditional beat-em-up, the player takes control of the nameless ninja. In cooperative two-player mode, the second player controls an orange ninja. Players fight a variety of enemies, using ninja attacks and combos. Due to the large amount of enemies at nearly all times, the game is incredibly difficult. During some battles, the player will be unable to move. At times, the player must use special abilities to reach places, such as acrobatics to reach different high up locations, and even walking on tightropes.