Shadow Dancer is a side-scrolling hack-and-slash action game produced by Sega and originally released as an arcade game in 1989. Versions released for the Amiga, Atari ST, Commodore 64, Amstrad CPC, and ZX Spectrum were published by U.S. Gold and developed by Images in Europe during 1991. More information on Wikipedia.

A trainer offers one or more cheats like unlimited lives, invincibility, more ammo etc. Because this is done during runtime a trainer is not to be confused with a savegame editor.