simple.css

*,
*:before,
*:after {
  box-sizing: border-box;
}

body {
  font: 18px/1.5 -apple-system, sans-serif;
  font-kerning: normal;
  text-rendering: optimizeLegibility;
  color: #333;
  max-width: 45em;
  margin: 2em auto;
  padding: 1em;
  overflow-x: hidden;
}

p {
  max-width: 33em;
}

a {
  color: royalblue;
}

img {
  width: 100%;
}