Examine source code of Undertale Surface

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Undertale Surface",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(229, 212, 0, 0.13)",
      "toolbar_text": "rgb(254, 251, 201)",
      "frame": "rgb(234, 194, 135)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgba(252, 168, 25, 0.1)",
      "toolbar_field_text": "rgb(245, 245, 222)",
      "tab_line": "rgb(252, 168, 25)",
      "popup": "rgba(86, 86, 40, 0.79)",
      "popup_text": "rgb(255, 167, 16)",
      "button_background_active": "rgba(86, 15, 63, 0.85)",
      "button_background_hover": "rgba(208, 117, 16, 0.78)",
      "frame_inactive": "rgb(86, 86, 40)",
      "icons_attention": "rgb(255, 152, 0)",
      "icons": "rgb(249, 209, 71)",
      "ntp_background": "rgb(43, 49, 23)",
      "popup_border": "rgba(255, 167, 16, 0.68)",
      "popup_highlight": "rgb(217, 141, 69)",
      "sidebar_border": "rgb(86, 86, 40)",
      "sidebar_highlight": "rgb(86, 86, 40)",
      "sidebar": "rgb(43, 49, 23)",
      "tab_background_separator": "rgba(255, 255, 255, 0)",
      "tab_selected": "rgba(172, 76, 0, 0.39)",
      "tab_text": "rgb(255, 255, 255)",
      "toolbar_field_border_focus": "rgb(255, 227, 255)",
      "toolbar_field_border": "rgba(255, 255, 255, 0.54)",
      "toolbar_field_highlight_text": "rgb(255, 255, 255)",
      "toolbar_field_highlight": "rgba(119, 5, 100, 0.91)",
      "toolbar_vertical_separator": "rgb(195, 9, 195)",
      "tab_loading": "rgb(252, 168, 25)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{88262e30-4f56-4ba2-828a-e725c0dd8152}"
    }
  }
}