:root {
  --primary: #337ab7;
  --success: #4caf50;
  --bg-color: #f6f9ff;
}
* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}
body {
  background-color: var(--bg-color);
  font-size: 16px;
  font-family: 'Nunito', sans-serif;
  width: 100%;
  height: 100vh;
  overflow-y: auto;
  overflow-x: hidden;
}
.btn-success,
.btn-success:active,
.btn-success:hover {
  background: var(--success);
  border-color: var(--success);
}
.btn-success:active,
.btn-success:hover {
  opacity: 0.8;
}
.question-header {
  background: var(--bg-color);
}
.question {
  display: none;
}