<header>
  <h1><a href="#">Logo here</a></h1>

  <input class="menu-btn" type="checkbox" id="menu-btn" />
  <label class="menu-icon" for="menu-btn">
    <span class="navicon" />
  </label>
  
  <nav class='menu'>
    <a class='nav-item' href="#">About Me</a>
    <a class='nav-item' href="#">Blog</a>
    <a class='nav-item' href="#">Contact</a>
  </nav> 
</header>

/* Adapted from https://codepen.io/mutedblues/pen/MmPNPG */

body {
  margin: 0;
}

header {
  display: flex;
  width: 100%;
  background-color: aliceblue;
}

header > * {
/*   flex-grow: 1; */
}

header h1 {
  margin-left: 1rem;
}

header a {
  text-decoration: none;
}

/* "Hide" checkbox -- moves it off screen*/
#menu-btn {
  position: absolute;
  top: -100%;
  left: -100%;
}

/* Hide hamburger for bigger screens */
.menu-icon {
  visibility: hidden;
}

.menu {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 250px;
  margin-right: 2rem;
}


/* Set width for mobile/smaller screen size. */
/* I set it big here so I don't have to shrink the screen so much */
/* for testing purposes */
@media screen and (max-width: 1100px) {
  
  header {
    display: grid;
    grid-template-areas:
       "title   title   hamburger"
       "nav     nav     nav";
  }
  
  h1 {
    grid-area: title;
  }
  
  .menu a {
    text-decoration: none;
    color: black;
  }

  .menu-btn {
    display: none;
  }

  .menu-icon {
    grid-area: hamburger;
    cursor: pointer;
    display: flex;
    justify-content: flex-end;
    align-items: baseline;
    padding: 30px 20px 30px 0;
    position: relative;
    user-select: none;
    visibility: visible;
  }

  .navicon {
    background: #333;
    display: block;
    height: 2px;
    width: 18px;
    position: relative;
  }

  .navicon:before {
    top: 5px;
  }

  .navicon:after {
    top: -5px;
  }

  .navicon:before, .navicon:after {
    background: #333;
    display: block;
    width: 100%;
    height: 100%;
    content: '';
    position: absolute;
    transition: all .2s ease-out;
  }

  .menu {
    grid-area: nav;
    max-width: unset;
    max-height: 0;
    transition: max-height .2s ease-out;
    overflow: hidden;
    margin: 0;
    padding: 0;
    background-color: #fff;
    display: flex;
    flex-direction: column;
  }

  .menu a {
    padding: 20px 20px;
    border-right: 1px solid #f4f4f4;
    background-color: #eee;
    width: 100%;
    text-align: center;
  }

  .menu-btn:checked ~ .menu {
    max-height: 240px;
  }

  .menu-btn:checked ~ .menu-icon .navicon {
    background: transparent;
  }

  .menu-btn:checked ~ .menu-icon .navicon:before {
    transform: rotate(-45deg);
  }

  .menu-btn:checked ~ .menu-icon .navicon:after {
    transform: rotate(45deg);
  }

  .menu-btn:checked ~ .menu-icon .navicon:before,
  .menu-btn:checked ~ .menu-icon .navicon:after {
    top: 0;
  }
}