Examine source code of Happy hearts

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Happy hearts",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(255, 255, 255, 0.75)",
      "toolbar_text": "rgb(0, 123, 195)",
      "frame": "rgb(255, 255, 255)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgb(255, 160, 219)",
      "toolbar_field_text": "rgb(255, 250, 130)",
      "tab_line": "rgb(255, 246, 0)",
      "popup": "rgb(255, 253, 222)",
      "popup_text": "rgb(119, 0, 72)",
      "popup_border": "rgb(118, 249, 255)",
      "tab_loading": "rgb(255, 246, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{94f86795-dcd5-41df-bd0d-040687e5e6bf}"
    }
  }
}