There are four game modes to choose from. In co-op you have Survival, Elimination, while multiplayer has it's own interesting take. Finally there is a single player mode which I don't suggest since this game is very difficult. For every game mode except for Single Player, sticking together as a team is crucial to winning. Being the lone gunner in most matches will most likely get you killed.
Design is where the game sets itself apart from other first person shooters. In survival mode there is a big emphasis on avoiding conflict from the robotic hoards. To start off you can hear the enemies walking in other rooms and running around the level will only cause enemies to hear you. Guns of course make loud noises so you can avoid this by attaching a silencer to your weapon. Though adding a silencer messes with the damage and aim a little. This is crucial since you don't want to catch the attention of every single robot in the building.
As a futuristic marine of course you have a helmet that tells you what's going on with the battlefield. It gives you locations of objectives, highlights friendly players, and lets you know how many bullets you have left in your clip. You can take off your helmet in order to see the world without any filter. Without your helmet on you won't be able to see any of the information it tells you. Why would you take off your helmet? Well when it rains on a certain level you can take off your helmet and see a bit further. This isn't necessary since the rain doesn't blind you to much. Also taking to much damage causes you your helmet to malfunction turning off all your indicators.
The final direction the game takes is with lighting. No matter which game mode you play levels change between darkness and light. As the map gets darker it's harder to see your enemies as well as for your enemies to see you. By turning on your flashlight you can see a little bit in front of you. When the light comes back on in the level you better hope you are not in the middle of a map.
Multiplayer also has an interesting take. Maps are based on controlling points and killing enemies. Once you die you can no longer respawn until one of your team mates captures a point. Though a match can be over once an entire team is killed or all the points are captured. Though each map has a time limit so once the time limit is reached the team with the most points wins the game.
Survival is the best game mode so far. You and four other friends have to turn on all the power sources on the map. The problem is that robots chase after you at great speeds and try and beat you to death. It's up to your and your team to stick together and turn on all the switches. Once you turn on all the switches make your way to the exit. The tension in this game mode is intense, and avoiding conflict is preferred then going in guns blazing.
Though here are my few problems with the game as a whole. No matter what you do in Interstellar Marines you earn points that go towards your overall rank. Though the rank really doesn't mean anything. Second problem I had is with the robots field of view during the night in Elimination. Even before I could see where they were on the map I felt like I got picked off from a distance by them, but maybe this is on purpose since they are robots they should have night vision.
Though with it's few flaws Interstellar Marines is well worth your money. Right now it's free to play so you should totally download it then purchase it since it is 66% off right now! This game is the perfect mix of challenge while offering a new take on realism as a futuristic marine. This game is in early access so they will have plenty more updates to come!