Counter-Strike is a modification (MOD) for Half-Life that is realism based. There are two versions of CS, Retail and Mod. Mod and Retail are basically the same except that Mod is free and does not include the training scenarios of the Retail version. The game has two teams, Terrorists and Counter-Terrorists. Each team will have different objectives depending on the map. The map types are: cs_ which is a hostage rescue map, as_ which are assassination maps, de_ which are bomb planting maps and es_ maps which are escape maps. The game is round based in CS meaning that if you die you might have to wait anywhere from several seconds to five minutes before you can play again.