After four parts,
Gameplay is pretty much what you are used to from. You traverse small mazes, open doors, push buttons to open even more doors, and then there are those doors which can only be opened using colour coded keys. Monster hordes are between you and the level exit, so you have to shoot your way through. Oh, yes, and health as well as ammunition can be restocked from supplies which just happen to lie around – just as new weapons, such power-ups are sometimes hidden in more or less secret rooms.
So roughly speaking, all this is in the tradition of the previousgames, which offered something similar from another graphical perspective. Or so you would think until you come to the details. The choice of available weapons, for example, is clearly inspired by the big IBM hit instead of its own predecessors. I.e. you run around with a shotgun instead of a machine gun. Which makes exactly zero sense in a science fiction game. Also, Giger-like aliens cannot be found anywhere. Instead, there are floating eyes, crawling demons etc. Ah, yes, and even the switches look identical.
Graphically, things unfortunately don't look so good. Not gloomy and atmospheric, as would be appropriate in a horror-themed game. In spite of the slow crawl on a standard A1200, only a very small part of the screen is actually used as gameplay-relevant window. The rest is taken by a large frame. Within this small main window, a particularly low resolution is used; all pixels are quadrupled, making everything look very coarse. Effectively, it consists of roughly 100x80 pixels blown up to a larger size. Very little to show any kind of detail.
Often, you will read comments that this can be accepted as gameplay, on the other hand, is spot-on. Partially, this may hold: even though you can only identify a monster when it is standing right in front of you, this is only an issue of visual attractiveness, because shots are aimed semi-automatically anyway; so the effect on gameplay is negligible. On the other hand, when you regularly miss branching corridors or stairs, because they can hardly be identified as such, there is really no way to defend this anymore. Just like when you fall into a pit, because you mistook it for just yet another undefinable colour blot.
It is a pity that Team 17 threw the mythology which they had built up over the years completely over board in favour of the attempt to imitate somebody else's successful product. It is inexcusable that this imitation just doesn't work at all. Even taking the typical gameplay restrictions found in this early genre for granted (limited mobility, semi-automatic aiming, repetitive level design etc.) – which could still be considered fair at the time –just doesn't deliver the minimum of playability. To put it bluntly, it is pixel trash bearing a somewhat popular name.