There is no conventional crosses, "halfbara" counter number of cartridges in the store and things like that.
Instead of all this is thought aspects such as:
aiming through the fly;
fire regime change;
realistic defeat soldiers from weapons (just one bullet in the head or torso);
the possibility to deviate to the side for sniping and more.
Realism has happened forces act accordingly: run from cover to cover, once again not to be put out and not yawn at the risk of being shot by the enemy will take you longer, and so on. N. It is worth noting that there is half the battle as never before - teamwork.
1. You need to download and install Steam http://steampowered.com/download/SteamInstall.msi
2. Go to your account or register a new one.
3. Go to the "My Games" and select "Activate via Steam ...", and enter the key received after payment.
4. Once activated, the game will appear in the game list (Library) and you can download it