Examine source code of Simple Memory

{
  "manifest_version": 2,
  "name": "Simple Memory Game",
  "version": "1.0",
  "description": "Match the cards before time runs out in this simple memory game.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ea2d53a1-ce13-4039-8279-39ffff871e29}"
    }
  }
}