Examine source code of playing mermaid

{
  "theme": {
    "images": {
      "theme_frame": "header.jpg"
    },
    "colors": {
      "frame": "#d6d6d6",
      "tab_background_text": "#fcfcfc"
    }
  },
  "version": "2.0",
  "name": "playing mermaid",
  "manifest_version": 2,
  "description": "a playing mermaid"
}