<div class="site">
  <header class="site-header"></header>
  <main class="site-content">
    <div class="left">
      <p>menu</p>
      <ul>
        <li>Top</li>
        <li>Page 1</li>
        <li>Page 2</li>
      </ul>
    </div>
    <div class="contents">
      <div class="menu">
        <div class="menu-list">
          <div class="menu-item">
            <button type="button" class="ghost-button" id="addButton">Add</button>
          </div>
          <div class="menu-item">
            <button type="button" class="ghost-button" id="deleteButton">Delete</button>
          </div>
        </div>
      </div>
      <div class="field">
        <div class="field-list" id="grid-list">
        </div>
      </div>
    </div>
  </main>
  <footer class="site-footer">
    <p class="footer-content"></p>
  </footer>
</div>

*, *:before, *:after {
	box-sizing: border-box;
}

html {
	height: 100%;
	font-size: 16px;
}

body {
	margin: 0;
	padding: 0;
	min-height: 100%;
	height: 100%;
}

.site {
	min-height: 100vh;
	height: 100%;
	display: flex;
	flex-direction: column;
}

.site-header {
	flex: none;
	height: 50px;
	padding: 5px;
	background-color: #444;
}

.site-content {
	flex: 1 0 auto;
	display: flex;
	padding: 0;
}

.site-footer {
	flex: none;
	height: 30px;
	margin: 0;
	background: #444;
}

.footer-content {
	margin: 0;
	padding: 0;
}

.left {
	width: 100px;
	background: #fac;
}

.contents {
	flex: 1;
	display: flex;
	flex-direction: column;
}

.menu {
  height: 40px;
	background-color: #d0f4ff;
}

.menu-list {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
}

.menu-item {
	flex: 0 0 24px;
	height: 24px;
}

.ghost-button {
	background: #eee;
	color: #444;
	border: 1px solid gray;
	border-radius: 4px;
	cursor: pointer;
	text-decoration: none;
	margin: 2px;
	padding: 0.5rem;
	outline: none;
}

.field {
	flex: 1 0 auto;
	background: #aea;
}

.field-list {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
}

.field-item {
	flex: 0 0 160px;
	max-width: 320px;
	height: 100px;
	border: 1px solid #666;
	background-color: #ffe;
}

@media (max-width: 380px) {
	.left {
		display: none;
		flex: 0 0 0px;
	}
}

@media (max-width: 320px) {
	.site, .site-header, .site-footer {
		width: 320px;
	}

	.contents {
		flex: 0 0 320px;
		background: #abe;
	}
}

window.addEventListener('load', function() {
  document.getElementById('addButton').addEventListener('click', function() {
    var item = document.createElement('div');
    item.className = "field-item";
    document.getElementById('grid-list').appendChild(item);
  }, false);

  document.getElementById('deleteButton').addEventListener('click', function() {
    var items = document.getElementsByClassName('field-item');
    if (items != null && items.length > 0) {
      for (var i = items.length - 1; i >= 0; i--) {
        items[i].parentNode.removeChild(items[i]);
      }
    }
  }, false);
}, false);