block3.css

html,
body {
  line-height: 1.5; // <- this will depend on your font
}

main {
  width: 50%;
  margin: 6% 25%;
}

@media (max-width: 768px) {
  main {
    width: 80%;
    margin: 15% 10%;
  }
}

@media (max-width: 350px) {
  main {
    width: 90%;
    margin: 15% 5%;
  }
}