After the End/Walkthrough

Campaign
While most levels in the game require a certain level of monsters to be completed, there are levels which require a different mechanic to be finished, here are some of them:


 * 1) Activate a switch, or several switches at once to say, deactivate a forcefield or unlock teleporters
 * 2) Kill the enemy leader or leaders
 * 3) Get the required object (Ship replacement levels, upon getting this the player can immediately leave)
 * 4) Destroy the required object (This could be a Mutant Spawner or Spawner Mutant)
 * 5) Get to the green circle before it disappears, or else you are stuck and all you can do is reset (Firing Range, Level 11)
 * 6) Survive for a few minutes as specified

Some of these requirements can be mixed up with each other, and most of these levels also definitely have a monster count that can be exhausted.

On Mission 72, the armored artificial mutant factory which is the boss can only be damaged by breaking the glass chambers surrounding it, any weapons will damage them except Mines to some extent, Flamethrower, Shocker, and Sonic Cannon, there are 2 Anti-Human Artilleries situated on both far sides of the factory so you have to be careful as these will damage you a lot while trying to destroy the chambers, once all glass chambers are broken the factory will stop creating mutants, but there will be a new mutant spawning points in the entrance to the factory and this new spawning point will create mutants fast, so you can either leave the mission now or stay for a while and kill more for extra score, the mutant hordes the factory creates while its active is pretty thick so weapons like the Sonic Cannon will have the spotlight here, Sentry Machinegun and Guardian will also help a lot.

On Mission 73, once you get close to the spaceship nearby, there will be a long green bar that appears right beside your ship replacement parts, as this long green bar depletes, the ship replacement parts you've collected will disappear as they are being installed to the ship, once the green bar is completely depleted the mission is done, and the game is completed.

Firing Range
Most levels in Firing Range will only ask you to kill a great amount of mutants, only 3 - 4 at most requires a switch to be activated, once you meet the requirements to leave out of the said level, get out as soon as possible.

Firing Range has a total of 40 levels, and while that may seem shorter and faster than Campaign, in reality this is actually not the case due to most levels/missions having a high kill count requirement, the skill you need the most in this mode is how to save your ammo and patience, you have to use what power-up is provided to you to the best that you can, you also need to have even better aiming for this mode, taking advantage of the environment around for free kills, such as leading the mutants to acid or lava to get free kills is also a good skill to learn and do in this game mode.

Survival
All 12 levels in Survival are never ending, the levels will contain different kinds of weapons that will be provided as well as different mutants to appear, there could also be environmental properties as well, learning how to deal with each and every mutant is one of the key skills you need to survive longer, as well as being able to use the weapons provided to you in the most efficient way possible, this will put your real skill on the game to the test.