Choose whether to play normal mode, put the bomb, or rescue the hostage. It also offers a zombie mode, in which you'll take the role of a zombie who has to infect the rest of enemies.
If you have ever played the original Counter Strike 1.6, you'll enjoy this version.
Remember you have to register for free in the official site.
Counter Strike Online is totally free and specially funny. It offers us a free way to shoot and enjoy plying one of the best shooters in videogame history.