This is a survival game. there are no objectives, no "kill Breen" all you have to do is survive. there are three major places, a junkyard, a combine base, and a zombie infected building. there are unlockable places, in which you need the code to get through. the codes are hidden around the levels. you get a small group of civilians who respawn at the start if they die.

the junkyard is a massive brawl between the citizens, the metro police, and the antlions. there are many cars and trees to take cover behind, but that doesn't save you in the end.

the combine base is a big fort by the lake. its just an outpost, so dont expect a huge warzone with missles and turrets. you need a key code to get in. You might find something useful in the parking lot.

The zombie infected area is the last place. in there, you will find an army of zombies and almost no light. If you go in, you will find DEATH!!


requirements:
zombie spawn points which can be found here: http://www.garrysmod.org/downloads/?a=view&id=52383

wire keypad
(you dont need wire though) found here: http://www.garrysmod.org/downloads/?a=view&id=43948

none of these files take up much room, i highly recommend you downloading them.
have fun killing.