* {
  box-sizing: border-box;
}

.main-heading {
  display: inline-block;
  float: left;
  margin-left: 20px;
}

.main-header {
  padding-left: 10px;
}

nav {
  text-align: center;
  display: inline-block;
  width: 500px;
  margin: 0 auto;
}

nav ul {
  display: inline-block;
}

nav ul li {
  display: inline-block;
  padding: 0 40px;
  margin: 50px 10px 10px 10px;
}