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
In Zombie Strike you have to survive 10 minutes on a deserted farm. You have several weapons weapons to shoot hordes zombies. Move with the WASD keys, aim and shoot with the mouse and choose another weapon with the number keys.