Headcrab Hunter 2 is a complete modification of Counter-Strike: Source. While it is similar to most zombie-based mods out there, it's also different in many ways. With this mod, you're dealing with something never seen before; headcrabs. They've invaded, and the Counter-Terrorist unit has been dispatched. Your mission is to survive the horde before time runs out.
As of v2.10, this mod has one gameplay mode; survival. However, the mod itself is very customizable. You can change nearly everything about the mod (headcrab health, human health, human, weapons menu, ammo amounts, etc.) with one simple configuration file. Conversely, if you're not so experienced with these things, leaving everything at their default values is just fine.
The game starts out with a single human, and three bots. By default, for every human, there is one headcrab, plus a default of two headcrabs - so two human players means 4 headcrabs, etc. There are three types of headcrabs: mothercrabs are slow, but have a lot of health and can kill most any human in nearly one hit; babycrabs are extremely fast, but have very little health and don't do as much damage; fathercrabs are a balance of the two and can spit harmful poison at their enemies, rendering them in a semi-unconscious state for a short while. Humans have somewhat of an advantage as they have access to an !guns menu by default, which allows them to select any class they'd like - assault, support, demolition, special ops, sniper, etc. - each comes with its own weapon pack, but teamwork is key, because one human cannot take on 10 or so headcrabs. Infection is enabled by default. With infection mode, a human who happens to be near a headcrab at the time of its death has a 1/8 chance of becoming an infected human (similar to a zombie) and joining the headcrabs until they are liberated, or killed by their fellow teammates. This inhibits camping as well as restricts players to areas bot headcrabs can get to. Of course, all of these features are optional and can be enabled or disabled at any time by server owners and operators.
This mod will work with nearly all maps. Default maps have been tested the most and are therefore highly recommended to be used, but the main script has been designed to change based upon the map being played. Any map that the plug-in doesn't recognize will result in the mod automatically adjusting to optimal values for a unique player experience every time. ZM, ZH, and ZE maps should all work just fine with this mod. Just make sure the map you wish to use has a .NAV file with it, as these NAV files control how bots move on a map. If an accompanying .NAV file is not present, CS:S will attempt to generate one for you, but they are not always very reliable.