The idea behind it is that you are in a VR combat simulation, and so your task is to grab the gun and find the exit to the level you are thrown into in the fastest way possible, and the simulation scores you on that. Hence, you run through the recreations of various docks and office buildings (there are 8 "biomes" and 34 maps in total), while also dealing with the machine gun and missile turrets in your way, all while watching the clock, since "your assignment is to be the best".
BIOS contains examples of the following tropes:
- Bottomless Magazines: Played with. The clip of your main gun has 20 bullets in it, but you can keep reloading it forever.
- Critical Existence Failure: The supposed VR combat simulation appears uninterested in simulating just what exactly happens to people once they get shot a couple of times with bullets or are hit with the shrapnel from a nearby missile.
- Defeat Equals Explosion: Both the turrets and the robots explode upon death, leaving nothing behind.
- Everything's Deader with Zombies: Each map can be played through with hordes of zombies replacing the turrets and the sci-fi soldiers.
- Fictional Currency: Beating maps gives you units.
- Gameplay Grading: You are only graded on time; your speed upon completing the level determines whether you get a Bronze, Silver, Gold or Platinum medal.
- Laser Hallway: Yellow lasers are present on some levels. The solution is to simply shoot at the edges of each beam.
- Laser Sight: Used by some turrets to aim.
- Mecha-Mooks: There are often robot soldiers backing up the turrets.
- Regenerating Health: Present. On the zombie levels in particular, it's often worth letting zombies scratch you a couple of times rather than stopping to shoot them, so that you can get to the finish faster and gain a higher score.
- Scoring Points: The primary motivation for playing the game.
- Weak Turret Gun: The turrets will all explode after a few bullets, in order to allow you not to spend too much time on them.