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

* {
  margin: 0;
  padding: 0;
}

body {
  width: 100%;
  max-width: 768px;
  min-height: 100vh;
  line-height: 1.5;
  margin: 0 auto;
  position: relative;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  width: 100%;
}

img[alt="header"] {
  position: sticky;
  top: 0;
  left: 0;
}

img[alt="footer"] {
  position: sticky;
  bottom: 0;
  left: 0;
}