In case you're unfamiliar, Counter-Strike is an entirely multiplayer experience. You can play offline against AI bots, but these are still merely simulating what it's like to play online, rather than really giving you a single-player game. The good news is that this is as good as online team-based shooters get. In the traditional game mode, there are two types of matches and two tiers of play. Casual level is for newer players and removes aspects like friendly fire and the need to purchase armor and ancillary items each round (more on that in a second). Ranked level is the original style of CS, with all the "realism" settings enabled, but it also features a comprehensive skill-based ranking system to try to balance teams and place good players with other good players.
Both of these tiers feature several maps--original CS maps like de_dust are reproduced here and still going strong, mixed in with entirely new maps--and each map is tied to one of two game types. In Defusal, one team (the Terrorists) must plant a bomb at a critical site and defend it until it explodes, while the other team (the Counter-Terrorists) must try to either prevent them from planting it or defuse it before it goes off. The other game type, Hostage Rescue, turns the tables. Here, the Terrorists have taken a group of AI hostages that they must protect until time runs out, while the CTs must assault their location and free the hostages.
One important facet to both of these game modes is that there are multiple short rounds in a match, and after each round you must purchase weapons, armor, grenades, and other equipment using money you earn for killing enemies, winning the round, or doing other important tasks. Thus, as games go on, winning teams tend to have better equipment, while losing teams tend to be worse off. The disadvantage is never insurmountable, but it does give teams an incentive to work, well, as a team. In serious matches, communication and planning are key, because players who die cannot respawn until after a round is over and cannot communicate with living team members.
The traditional CS modes are excellently balanced. Games are fast-paced without being unmanageable, skill is rewarded in both the planning and outfitting stages as well as in battle, and good teamwork typically beats individual skills. Pacing is fantastic, too, because you will generally die at least a few times, giving you time to observe other players' work, review your own mistakes, and plan for the next round during the downtime. Heck, even watching other players go at it can be entertaining in and of itself, as you shout at them to do this or not do that, knowing full well they can't hear you.
If you prefer no downtime, however, the two new game modes that have been added this time around should suit your fancy. Called Arms Race and Demolition, they both remove the classic purchasing mechanic and instead award you with a new weapon, instantaneously, when you make a kill. Depending on server settings, weapon awards generally go up in deadliness from an initial lousy weapon, reach an acme, and then begin to go down in usefulness, usually forcing you at last to use nothing but your knife.
Installation information:
1. Mount image
2. Run setup.exe
3. Follow the instructions of the installer
System requirements:
Operating system: Windows XP / Vista / 7/8
Processor: Pentium 4 3 GHz or dual core from Intel with a clock frequency of 2 GHz / AMD64X2
Memory: 1 GB (XP) / 2 GB [ Vista / 7/8 ]
Video Card: 128 MB VRAM compatible with DirectX 9.0
and the technology to support Pixel Shader 2.0b
(ATI Radeon X800 or better / NVIDIA GeForce 7600
or better / Intel HD Graphics 2000)
Sound card: compatible with DirectX 9.0c
Free space on hard disk: 10 GB