The BBC version of Ultimate‘s classic Nightshade is very good. It runs pretty quickly (most of the time) and the controls are responsive, which is all you can hope for in the game like this.
For some reason it doesn’t have the border around the play area, or the container for the antibodies like in the original Spectrum version, but that doesn’t affect the gameplay. It does mean, though, that the screen looks a bit bare, and the play area tiny, but it’s the same size play area as the Spectrum original.
The aim of the game is to destroy four demons that are terrorising a village, and each one requires a special weapon to do that. It’s a daunting task, especially as all the villagers have been turned into monsters and will damage you if they touch you. Thankfully you can collect antibodies inside houses and shoot them at the monsters to destroy them. You must use the correct antibody on the monsters to destroy them; use the wrong one and it might clone the monster and make two of them! Defeating the four demons is a different matter, though. If you manage to find any of the four special weapons needed to kill them, the correct weapon will flash when you are near the associated demon. Firing the correct weapon at a demon will kill it and earn you a stack of points. Then you must do the same for the remaining three.
Nightshade is one of those games where you can have fun just wandering around aimlessly, shooting things. If you want to complete the game, however, you’re probably going to need a map and emulator quicksaves.
More: Nightshade on Wikipedia