@IBAction func answerButtonPressed(_ sender: UIButton)
    {
        let userAnswer = sender.currentTitle!
        let actualAnswer = jsonData.classes![0].calculus![questionNumber].answer

        if userAnswer == actualAnswer {
            sender.backgroundColor = UIColor.green
        } else {
            sender.backgroundColor = UIColor.red
        }

        if questionNumber < jsonData.count - 1 {
            questionNumber += 1
        } else {
            questionNumber = 0
        }


        Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(updateUI), userInfo: nil, repeats: false)
    }