index.css

body {
  background-color: lightgrey;
  font-family: 'Open Sans', sans-serif;
}

h1 {
  text-align: center;  
}

.clicktostart {
  text-align: center;
}

.titleimage {
  display: block;
  margin: auto;
  width: 70%;
  height: 70%;
}

.startbutton {
  margin: auto;
  left: 0;
  right: 0;
  margin-top: 20px;
  display: block;
  padding: 5px;
  border: 1px solid grey;
  width: 100px;
  height: 50px;
  border-radius: 3px;
}

.answer, .next-question, .final-score, .playagain {
  width: 120px;
  height: 60px;
  display: block;
  font-size: 1.1em;
  border-radius: 3px solid grey;
  background-color: lightgrey;
  
}

@media only screen and (max-width: 640px) {
body {
  width: 100%;
  }
}

.questionnumber {
  text-align: center;
  font-size: 1.2em;
}

.questiontitle, .score-tab, .correct-answer, .incorrect-answer, .quizresults {
  text-align: center;
}

.answer, .next-question, .final-score, .playagain {
  display: block;
  margin: auto;
  background-color: white;
}

.questionbox {
  display: block;
}