{
    "title": "Survey Title Here", // the survey title
    "pages": [ // a sequence of pages
        {
            "lines": [
                "first line", // plain text that will be displayed
                "second line {foo}" // displays: second line bar
            ],
            "vars": { // defines local variables
                "foo": "bar"
            },
            "pid": "start" // the id for the page (used as prefix in the result file)
            "continue": "next", // creates a single button at the bottom -- default ("next") can be omitted
            "type": "plain" // the type of page -- default ("plain") can be omitted
        }, {
            "type": "each", // repeats a sequence of pages
            "name": "ix", // the iteration variable name -- it can be used via {ix} in fields
            "vars": { // defines local variables
                "img_len": 25 // we define the range as variable so we can use it in the text
            },
            "to": "{img_len}", // iterate until this number
            "pages": [
                // ... pages to repeat ...
                {
                    "lines": [
                        "image {ix} / {img_len}", // displays: image 0 / 25
                        [ "img", "path/to/image{ix}.png", "" ] // the image to display
                    ],
                    "pid": "question:{ix}" // the id for the page
                    "continue": "choice", // creates a collection of buttons at the bottom
                    "values": [ // the values to choose from
                        "yes",
                        "no"
                    ]
                }
            ]
            // this page type does not have a "continue" field
        }, {
            "lines": [
                // other special lines
                // [ question_type, display_text, question_id ]
                [ "text", "just text", "" ], // simple text -- equivalent to "just text"
                [ "likert", "fun", "fun" ], // likert scale
                [ "likert", "confidence", "conf" ]
            ],
            "pid": "specials"
        }, {
            "lines": [
                "Thanks! {_token}" // _token is a special variable containing the user id
            ],
            "continue": "end", // indicates the end of the survey -- this page must exist
            "pid": "end"
        }
    ]
}