* {
  box-sizing: border-box;
}
html, body {
  padding: 0;
  height: 100vh;
  width: 100vw;
  overflow: hidden;
  display: block;
  box-sizing: border-box;
}
html {
}
body {
  margin: 10px;
  padding: 10px;
  height: calc(100vh - 20px);
  width: calc(100vw - 20px);
  font-family: sans-serif;
  border: solid 1px purple;
}