Examine source code of Mars Sunset

{
  "theme": {
    "images": {
      "theme_frame": "MarsSunset_h2.jpg"
    },
    "colors": {
      "frame": "#949494",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Mars Sunset",
  "manifest_version": 2,
  "description": "The Sun setting on Mars.\nImage taken by NASA's Spirit Rover at Gusev crater"
}