Counter-Strike Online (CSO) is a game in the Counter-Strike series targeted towards Asia's gaming market. It was developed by NEXON Corporation of South Korea with oversight from license-holder Valve Corporation. It uses a micropayment model that is managed by a custom version of the Steam back-end.
Counter-Strike Online features some old game modes from the previous games in the series as well as new ones, modified version of custom modes:
- Team Deathmatch
- Basic Mode
- Clan Match
- Zombie: The Original
- Zombie: The Mutation
- Zombie: The Hero
- Zombie: The Hero: The Origins
- Z-VIRUS: Angra
- Zombie: The Union
- Zombie Scenario: Survival
- Zombie Scenario: Pursuit
- Zombie Scenario: Annihilation
- Zombie Scenario: Season 2
- Zombie Scenario: Season 3
- Zombie Shelter mode
- Human Scenario: Annihilation
- Human Scenario: Pursuit
- Metal Arena
- Skill Challenge
- Fun mode: Hidden
- Fun mode: Zombie Escape
- Fun mode: Bazooka Battle
- Gun Deathmatch (Gun Game)
The game also features a variety of additions over the international games, such as an introduction to female characters, numerous new weapons and skins for previous weapons. Most of the weapons are "locked" by default, so cash points or game points are essential to purchase them. Cash points are purchased through real-world money for special weapons, skins, power-ups, etc. You can also buy standard weapons for periods of time using game points earned from playing the game.
The players compete each other to get the highest kill. After death, the player will respawn randomly on the map in 5 seconds and invincible for 3 seconds.
Counter-Terrorists compete with Terrorists to get the highest kill score. No specific goal and the players will respawn in 5 seconds and invincible for 3 seconds after death.
Zombie: The Original
Zombie: The Original closely follows the popular, unofficial mods of Zombie Mod - specifically, Infection mode.
Zombie: The Mutation
Zombie: The Mutation introduces supply box for humans, which include exclusive special weapons and new zombie types for zombie team. The zombies are:
- Light zombie (Female zombie, Sarah)
- Heavy zombie (Fat male zombie, Uncle Dai)
- Psycho zombie (Dead surgeon and doctor)
- Voodoo zombie (African witch doctor)
- Deimos (Alien zombie)
- Ganymede (Mutated alien zombie)
Zombie: The Hero
Zombie: The Hero introduces Morale Bar for humans which can increase attack damage for humans by 10% with each zombie kill while for the zombies, they will revive after death unless headshot. The new zombie introduces are:
- Stamper (Undertaker zombie)
- Banshee (Witch zombie)
- Jiang Shi (Chinese zombie)
Z-VIRUS is the second patch for Zombie: The Hero, with new zombies and weapons. In the recent trailer, Choijiyoon was attacked and fled from Sting Finger and Venom Guard. Choijiyoon can be seen armed with an M32 MGL. The zombies are:
- Sting Finger (Female Researcher, Choijiyoon's sister)
- Venom Guard (Male Security Guard)
Challenge Mod closely follows "Fun" maps, where players compete in scenarios utilizing jumping, running, bunny hopping, and/or surfing to get to the end of the level.
Zombie Scenario: The Survival
The second new gameplay mode is Zombie Scenario Mod, which pits up to 10 players against increasingly harder waves of AI controlled zombies. You are able to buy extra health and damage if you have enough money. The levels keep getting harder with zombies having more health and abilities. A new zombie is revealed in this mode and called the Juggernaut. He is an evolved Heavy zombie and is twice the size of it, and holds a weapon that deals more damage than a normal zombie attack. This mode was released in December 9, 2009.
Zombie Scenario: The Pursuit
Nexon released a new map called "Last Clue" on January 27th. There are only 2 rounds for this map. The first round requires all players to break through obstacles while battling attacking zombies at the same time. Unlike the other Zombie Scenario maps, players can spawn at the nearest checkpoint, but they have to wait 60 seconds or 1 minute. Once all the obstacles have been broken and half of the players reached the checkpoint, the second round starts. This round presents a difficult Alien Boss called as Phobos with many different attacks. After a set amount of time, normal zombies start appearing, creating an even harder challenge.
The second map is called "Chaos". The players have to face mazed underground laboratory to go for the surface. Once on the surface, the players have to defeat Siege-type Phobos.
The third map is called "Dead End". The players have to go through expanded version of Havana to find and defeat the new boss called "Oberon".
- Main article: Assassination
Nexon released a mode from the original Counter-Strike called VIP Mode. The Counter-Terrorists try to escort the VIP safely to a designated safety area or eliminate all Terrorist forces in the map. The Terrorists are to assassinate the VIP before he gets to the chopper or wait until time runs out. The map “Oilrig” was the first of many new VIP maps to be released. The VIP carries double armor and only a USP with 24 bullets in reserve.
World Cup 2010
On May 25th, Nexon released a new game mode called World Cup 2010 in conjunction with the 2010 FIFA World Cup. Includes 2 new soccer maps, 2 football types and new character skins. The main objective is basically to score points by kicking the ball into the oppositions goal. Players are allowed to purchase items and stab enemies during the gameplay.
Fun mode: Hidden
Hidden was released on 1st week of January 2012. The first player who reaches the target kills wins the game. Hidden follows an unofficial Half-Life 2 mod, The Hidden. In Hidden, a player will be chosen as the Joker and needs to eliminate the other players. The Joker has 300 health points and will be fully invisible when stationary while half-invisible when moving.
Fun mode: Zombie Escape
The humans must escape from the zombies by reaching a boat. This mode is round-based and has the limit of 10 players per room. In this mode, one player will be chosen as the Host zombie and must infect all humans and prevent it from reaching the escape zone. The humans that succeed reaching the escape zone will be safe while the late one will be left behind and died.
Fun mode: Bazooka Battle
Bazooka Battle was released on January 31, 2012 for Korea server. In this mode, the players can only use Bazooka and must eliminate the opposing force. The players in this mode can move faster than usual.
Gun Deathmatch is based on a Counter-Strike mod, Gun Game. This mode was released on March 2012, as the response of a new Counter-Strike: Global Offensive mode, Arsenal. the gameplay is similar to the Gun Game, except with several modifications.
The default models are reused from Counter-Strike: Condition Zero.