The story mode is split into 5 chapters which see Conrad navigate through the corridors and rooms of a spaceship, eliminating any aliens that stand in his way. The story across the three games isn't well developed, but all you need to know is that Conrad works his way through a spaceship which is infested with aliens.
The voice acting within the game is pretty minimal and usually resorts to displaying text on the bottom area of the screen. It's not a huge deal when there's no action, but often lines are missed because you are focussed on shooting.
You navigate Conrad around the ship, guided by way-points marked on your map. The frequency of way-points mean you can never get lost and therefore concentrate on shooting. If you do notice open doors, you can venture off track in order to find extra pick-ups. These include ammunition, grenades, health packs and credits. Credits can be spent on a few upgrades or purchase extra ammunition from the terminals where you save your progress.
Conrad is usually given an objective to interact with the ships mechanisms; but it's never that simple. You may have to take a detour and complete sub-objectives instead, or an alternate plan is given. For example, you may be given an objective to restart a generator, but it fails to start, so then you need to power-up the back-up system instead. As far as you're concerned, you just follow the new way-points and shoot anything in your path.
As Conrad moves around the corridors, there's plenty of explosions which is a nice visual effect which illustrates the ship's poor state and makes use of the game's lighting model. The corridors are pretty dark and you need to make use of the light Conrad has on his gun. There's plenty of aliens popping up through the floor, or bursting through the walls to try and ambush you. Although it's not a scary game per-se, the aliens charging in suddenly could be considered a jump-scare at times. However, if you have played the other games in the series, nothing will surprise you by this stage in the story.
At the start of the game you are equipped with a few weapons. A basic pistol with unlimited ammunition, a machine gun, and a shotgun. As you progress through the game, you are given new guns which include a flame-thrower, chain gun and 'Project X'. These weapons have limited ammunition, so you have to use them more sparingly. On the plus side, they are far more powerful than the basic pistol. The general strategy is to try and conserve ammunition when there's little threat, especially when you encounter the smaller aliens that can be taken down with one pistol shot. When the threat is greater, you switch to the big guns to quickly eradicate the horde.
I opted for the default controls which is using WASD to move, and the mouse to aim. Left-click shoots, right-click uses secondary equipment like health packs and grenades. R is used to reload, Z/X scrolls through the secondary equipment, mouse-wheel scrolls through guns. Q/E quickly pans the camera, or you can use the mouse (move to edges of the screen). You can run with Shift but Conrad cannot aim whilst running and fatigues with continued use; so is only used in short bursts. Ctrl gives a mêlée attack if the aliens are in close proximity.
On occasions, the perspective can change and be locked; which is basically an attempt to add variety to the game. These sections are extremely awkward and clunky; you don't have a great view of your surroundings and it becomes less accurate to aim; I despised these sections.
I found that I was frequently walking into objects in this game which I put down to awkward design. I don't recall this being a huge problem in the previous games. Another annoying aspect is how the main villain Klein frequently talks to you. He has stereotypical dialogue and cliché evil laugh which is pretty cringe-worthy. There's a lot of areas which are flooded by water which seemed an overused mechanic. I found the aliens much harder to spot when they are in water, so I found my health draining fast in these sections.
The game's ending was very disappointing. I guess you can't expect the story to have a great conclusion when the story was never a great aspect of the game. However, the strategy to take down the boss was boring. I was just backing off in a circle whilst mindlessly shooting, using medi-packs when I had a second spare.
Although it's part of a trilogy, it's not really a big deal to jump into the series at any instalment. I found this game to be the worst though. It seemed the new ideas simply made the game worse, so the series concludes on a bit of a low note.