Examine source code of Ultrakill

{
  "manifest_version": 2,
  "version": "2.0",
  "name": "Ultrakill",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(52, 49, 128, 0)",
      "toolbar_text": "rgb(88, 255, 248)",
      "frame": "rgb(29, 26, 53)",
      "tab_background_text": "rgb(158, 226, 43)",
      "toolbar_field": "rgba(144, 0, 134, 0.5)",
      "toolbar_field_text": "rgb(158, 226, 43)",
      "tab_line": "rgb(88, 255, 248)",
      "popup": "rgb(62, 20, 40)",
      "popup_text": "rgb(158, 226, 43)",
      "ntp_background": "rgb(29, 26, 53)",
      "ntp_text": "rgb(158, 226, 43)",
      "tab_loading": "rgb(88, 255, 248)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{112b8354-aa67-4fe9-a7f4-03e6d18e8842}"
    }
  }
}