Deep gameplay, great mood and music makes Zero Tolerance overshine what it lacks.
Start up
The story is about some alien invasion somewhere in space, and therefore some government sends in a group of elite space marines. When you start the game you get the briefing, then you get to choose which character you want to play as. They all got different skills; martial arts skills(you can both punch and kick in this game), explosives skill , marksmanship and so forth.
Game play
The first couple of levels are rather boring, since you'll only be fighting some kind of zombie-soldiers. But after that, you'll start to encounter all kinds of aliens, some of them are rather creepy.....Or at least they were in 1994. So the game gets better and better. You'll encounter creepy aliens, use different gadgets, night-vision, fire extinguisher( to clear a path in some burning rooms), explosives, bullet proof vest, bio scanner(puts all enemies on your radar), fire suit and flashlight. The game is rather long, it took me a long time to complete. The game uses a password save system.
Another great thing is that you get to fight MANY enemies at once in some of the bigger rooms. When you enter a level, you can see how many enemies there are on your hud display. The hud also displays your health in numbers. It also displays your inventory, radar and the character you play as. When you die, your character is dead, meaning you choose the next character available. But I just reload the map instead.
Weapons
The weapons have a rather cool design, you start off with a handgun(of course). You'll find the shotgun right at the beginning of the game. As you start to encounter the aliens, you'll also start to find more interesting weapons, although there isn't many; Flamethrower, hand grenades, mines, laser aimed gun( laser-point sight and full auto if you hold button), pulse laser, and rocket launcher.
Sound
The sound is very good in the game. The guns sound cool and satisfying. The music is great with it's moody and maybe sometimes creepy style. The aliens sound creepy, which is great in my opinion.
Graphics
Although lacking in texture, the game has rather ok graphics including walls cracking up when you shoot at them, nice views of space through massive windows that line up as walls in some rooms. Level design is one floor per level, there are no stairs. You finish a level by killing everyone(otherwise that level is not actually finished) and then entering an elevator. You can move back to finish levels later if you wish, just go to the elevator. It's a neat changing level effect, since there isn't any score screen or anything between a level, you just stand in the elevator as it moves whilst a nice music tone plays.
The enemies are as detailed as the graphics allow them to be, but don't worry, you can clearly see the difference between them.
Overall
This game is great, not exactly the same rock n' roll style that Doom has going, but rather a more mood setting alien blasting that gives you the feeling of really being in space...on a space station. With the much deeper game play than Doom, these two games rank up equally but in different ways. So if you can overlook the lacking textures(but still nice graphics), and you like Old School fps, play this game.