Verify on server side

[dunghy7]

public bool Verify([FromBody] List<string> datas)
        {
            var value = JsonConvert.DeserializeObject<List<int>>(datas[0]);
            var sum = value.Sum();
            var avg = sum * 1.0 / value.Count;
            var stddev = value.Select(v => Math.Pow(v - avg, 2)).Sum() / value.Count;
            return stddev != 0;
        }

When slide image successful or unsuccessful, always return the number greater than 0

[jcmichot]

I confirm, same with javascript inside _proto.verify = function ()

        var sum = function (x, y) { return x + y; };
        var square = function (x) { return x * x; };
        var average = arr.reduce(sum) / arr.length;
        var deviations = arr.map(function (x) { return x - average; });
        var stddev = Math.sqrt(deviations.map(square).reduce(sum) / arr.length);
        verified = stddev !== 0

"verified" is always TRUE.
Only javascript "spliced: Math.abs(left - this.x) < this.options.offset" is usefull to confirm valid captcha.

That's a nice captcha but need to be secure with real server side feature.