style.css

body {
  font-family: "Lucida Sans", Arial, sans-serif;
}

.header {
  height: 65px;
}

.header-inner {
  width: 100%;
  margin-left: auto;
  margin-right: auto;
}

.side-menu {
  height: 100%;
  width: 200px;
  position: fixed;
  top: 0;
  left: 0;
  background-color: #55991155;
  overflow-x: hidden;
  padding-top: 20px;
}

.side-menu a {
  padding: 9px 8px 6px 16px;
  text-decoration: none;
  font-size: 20px;
  color: #111;
  display: block;
  width: 100%;
  text-align: left;
}

.side-menu a:hover{
  background-color: darkgray;
}

main {
  margin-left: 200px; 
  font-size: 20px; 
  padding: 0px 10px;
}

@media screen and (max-width: 450px) {
  main {
    margin-left: 0px;
  }

  .side-menu {
    -webkit-transform: translate(-600px, 0);
    transform: translate(-600px, 0);
    width: 100%;
    z-index: 10;
    position: absolute;
    margin-top: 65px;
    background-color: white;
  }

  .side-menu a {
    text-align: center;
  }

  .side-menu.open {
    -webkit-transform: translate(0, 0);
    transform: translate(0, 0);
  }

  .header__title {
    margin-left: 0;
    font-size: 2em;
    vertical-align: bottom; 
  }

  .header-menu {
    display: inline-block;
    position: absolute;
    right: 0;
    padding: 1em;
  }
  .header-menu svg {
    width: 32px;
    fill: #E0E0E0;
  }
}

@media screen and (min-width: 450px) {
  header {
    display: none;
  }
}