Fight For Life is an expansion for Alien Shooter, so the player should not expect much in the way of technical improvements. Unfortunately, the player should not expect much in the way of fixes either.
The view obstruction issue in the original game due to the rigid isometric camera has not been addressed in any way. The deficiencies in the aliens' pathfinding and shooting A.I. have not been addressed either. The designers still intend to use them to the game's advantage, so players who have been irked by these issues may want to skip this expansion altogether.
For those that would persevere, they would notice that there is a sequel to the "Story" mode. Of course, this is just an excuse to shoot up some more aliens; the additions to the backstory isn't that exciting and not much of a surprise.
Despite the player character's effort in the original story, the aliens managed to break out of their prisons in research bases around the world. They proceeded to overrun Earth, though the human survivors apparently were resourceful enough to consolidate and concentrate themselves in somehow more defensible communities. Of course, these communities are still at risk of being attacked, or in the case of the one that the player character would be inserted into in the expansion, at risk of being victims of accidents of their own making.
The expansions appears to start out the same way as the original: the player character is placed onto the ground level of a base and has to go deeper to the source of the problem. However, it will become apparent quickly that the expansion is meant for an experienced Alien Shooter player; the first level alone will spawn aliens that appeared in the first half of the levels in the original story.
However, the player also discovers that the challenge provided by that is just too short; the number of levels in the expansion is far less than those found in the original story. There are no new objectives to be had either; they still concern shooting every alien in the level and/or blowing teleporters and generators.
The aliens and weapons have been retained over from the original game with no new additions, which is perhaps the biggest disappointment.
However, the levels appear to be better designed. There are no more boring corridors that would be filled with tides of aliens, though there are still plenty of aliens. There are also new furnishings for levels, which contribute to the thematic quality of the levels.
On the other hand, the more detailed level designs give stark reminders that the aliens' pathfinding A.I. is still pathetic; aliens will struggle to work their way around school-desks, shelves and lockers, to cite an example. The new furniture also blocks shots, either from the aliens or the player character, which can be a bother. Their hitboxes are not simple either, thus leading to some unpleasant surprise when a player finds out that a rather large obstacle may not be a piece of reliable cover from certain angles.
There are some interesting levels, such as a warehouse that is filled with explosives and fuel barrels, which have to be used to defeat the swarms of aliens in said level as the player character happens to lack powerful weapons. There are other desperate situations like this, which somewhat pay homage to the name of the expansion.
Overall, Fight For Life would not have been a worthwhile purchase during its time, back in 2004/2005, especially not with its rather limited content and almost nothing new that is noteworthy. However, as part of a bundle, such as Good Old Games' package for Alien Shooter, it may be worthwhile, but only to those that have yet to play the game.