The absolute most barebones of a functional team shooter – but an important milestone of gaming history and technological innovation, a welcome addition to any Steam Library.
What originally started as a loose collection of sprites and models forged from the multiplayer component of Valve’s GoldSrc Engine by doting fans has gone to become one of gaming’s most famous success stories.
The final build update of the original Counter-Strike mod, or “1.6” as it is known by fans, is now preserved for posterity and our enjoyment alongside more recent instalments in the series, available separately, or bundled alongside the Condition Zero bundle, with that game and it’s official expansion-campaign. 
Gameplay is very simple, but belies a massive potential skill ceiling; two small squadrons of terrorists and counter-terrorists meet head-on and must either eliminate each other in a tense deathmatch, or use every ounce of their cunning to surreptitiously meet another objective such as bomb placement (terrorist), or bomb defusal and hostage rescue (both counter-terrorist) on one of twenty-five different maps.
The barebones nature of the game does afford it a great deal of easy-to-learn simplicity, and makes it easy to run on any rig, however, it is not without downsides – for those more inclined towards solo play might find the complete absence of a dedicate singleplayer mode whatsoever and no native bot support disappointing. Some ease-of-use features developed for sequential games that have become familiar to players newer to the series might also find the lack of these features difficult to adjust to, if they plan on visiting the first game in this now-venerable franchise for the first time with little idea of what to expect. 
In addition, while this game has retained a very dedicated and persistent fanbase in the eighteen years since release, the amount of active players and functioning servers is slowly declining, and one might find it hard at times to find populated servers. 
While lacking Steam Trading Cards or Achievements, this is still clearly a title Valve are not letting go off anytime soon, having come this far; a game this enjoyable and mechanically sound is worth a look, especially if you have the fortune to spot it while on sale or bundled alongside other games in the series.