@media (max-width: 767px) {* {
  box-sizing: border-box;
}

#nav, .submenu li {
  list-style: none;
  margin: 0;
  padding: 0;
}
html, body {
  min-height: 100%;
}

a {
  text-decoration: none;
}

.main-header {
  background: linear-gradient(#3f94bf, #246485);
  padding: 5px;
  text-align: center;
  color: white;
  text-shadow: #222 0px -1px 1px;
  position: fixed;
  width: 100%;
  left: 0;
  transition: all 0.3s ease;
}
.main-header a {
  position: absolute;
  left: 20px;
  top: 20px;
  color: white;
  font-size: 32px;
}

.page-wrap {
  float: right;
  width: 100%;
  transition: width 0.3s ease;
}

.main-nav {
  position: fixed;
  top: 0;
  width: 0;
  height: 100%;
  background: #3B3B3B;
  overflow-y: auto;
  transition: width 0.3s ease;
}
.main-nav a {
  display: block;
  background: linear-gradient(#3e3e3e, #383838);
  border-top: 1px solid #484848;
  border-bottom: 1px solid #2E2E2E;
  color: white;
  padding: 15px;
}
.main-nav a:hover, .main-nav a:focus {
  background: linear-gradient(#484848, #383838);
}
.main-nav:after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  height: 100%;
  width: 34px;
  background: linear-gradient(to right, rgba(0, 0, 0, 0), rgba(0, 0, 0, 0.4));
}

.content {
  padding: 100px 20px 20px 20px;
}

.close-menu {
  display: none;
}

#main-nav:target {
  width: 20%;
}

#main-nav:target + .page-wrap {
  width: 80%;
}
#main-nav:target + .page-wrap .open-menu {
  display: none;
}
#main-nav:target + .page-wrap .close-menu {
  display: block;
}
#main-nav:target + .page-wrap .main-header {
  width: 80%;
  left: 20%;
}
}