Chrome 42+ disables NPAPI plugins like Unity3d plugin.
Copy and paste the following text into your browser: chrome://flags/#enable-npapi and enable the NPAPI plugin.
Or try another browser like Firefox
Take control of Swat members or Mercenaries (zombies). Which side do you choose? Join a server and try to kill the enemy. Aim and shoot with the mouse, walk with the WASD, run with Shift, choose your weapon with 1-5.