Examine source code of Herozero Style Changer

{
  "manifest_version": 2,
  "name": "Herozero Style Changer",
  "description": "This addon changes style of the herozerogame.com site. It will change the background to dark, and generally will make the site to look better on lower resolution displays, by removing unnecessary elements.",
  "version": "1.2resigned1",
  "permissions": [
    "tabs",
    "activeTab",
    "http://herozerogame.com/"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*.herozerogame.com/*"
      ],
      "js": [
        "script/main.js"
      ],
      "css": [
        "script/main.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8bd8d692-a8d4-488b-b8f7-5cc287ba0fbd}"
    }
  }
}