Examine source code of Sound Memory

{
  "manifest_version": 2,
  "name": "Sound Memory",
  "version": "1.0",
  "description": "Memory game where different tabs/elements produce distinct sounds. Memorize the sequence and replay it.",
  "icons": {
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "storage"
  ],
  "web_accessible_resources": [
    "soundmemory.html",
    "soundmemory.js",
    "soundmemory.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{25b3adc2-bcca-4880-a812-e54073f60c49}"
    }
  }
}