Examine source code of Boomer

{
  "manifest_version": 2,
  "name": "Boomer",
  "version": "0.2",
  "description": "A game for the browser.",
  "icons": {
    "48": "icons/boomer-48.png"
  },
  "browser_action": {
    "default_icon": "icons/boomer-32.png",
    "default_title": "Boomer",
    "default_popup": "popup/boomer.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e2e7a312-9935-4b84-a565-c81cf8c0b649}"
    }
  }
}