Examine source code of periodic

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "periodic",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "left bottom"
      ],
      "additional_backgrounds_tiling": [
        "repeat-x"
      ]
    },
    "colors": {
      "toolbar": "rgba(131, 15, 229, 0.22)",
      "toolbar_text": "rgb(45, 236, 17)",
      "frame": "rgb(45, 236, 17)",
      "tab_background_text": "rgb(45, 236, 17)",
      "toolbar_field": "rgba(73, 46, 153, 0.17)",
      "toolbar_field_text": "rgb(45, 236, 17)",
      "tab_line": "rgb(255, 30, 0)",
      "popup": "rgb(8, 3, 13)",
      "popup_text": "rgb(131, 15, 229)",
      "tab_loading": "rgb(255, 30, 0)"
    }
  }
}