materio-d8/web/themes/custom/materiotheme/assets/styles/base/_fonts.scss

body{
  font-size: 16px;
  font-family: "Ubuntu",Arial,"MS Trebuchet",sans-serif;
  font-weight: 500;
  font-style: normal;
  line-height: 1.3;
}
a.btn{
  display: inline-block;
  font-size: 0.9em;
  font-weight: bold;
  padding: 0.7em 1em;
  margin-bottom: 0.3em;
  background-color: #fff;
  color: #000;
  border-radius: 5px;
}