Midnight Resistance is a side-scrolling action shooting game produced by Data East for the arcades in 1989. The game was ported by Data East to the Sega Mega Drive in 1990 and by Ocean Software to ZX Spectrum, Amstrad CPC, Commodore 64, Commodore Amiga and Atari ST during the same year. More information at 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.