html{
  background-color: aliceblue;
}

body {
  display: block;
  width: 900px;
  margin: 0 auto;
}

#myDIV h2{
  margin: 30px;
  color: aliceblue;
  text-stroke: 1.2px #333;
  -webkit-text-stroke: 1.2px #333;
  font-size: 32px;
  text-align: center;
}

/* Include the padding and border in an element's total width and height */
* {
  box-sizing: border-box;
}

/* Remove margins and paddings from the list */
ul {
  margin: 0 40px;
  padding: 0;
}

/* Style the list items */
ul li {
  cursor: pointer;
  position: relative;
  padding: 12px 8px 12px 35px;
  list-style-type: none;
  background: #ddd;
  font-size: 18px;
  transition: 0.2s; /* スタイル変更終了までの時間 */
  user-select: none;
  color: #333;
  border: solid 1px gray;
}

/* Set all odd list items to a different color (zebra-stripes) */
ul li:nth-child(odd) { /* :nth-child 擬似クラス=状態を指定 */
  background: #ddd; /* 背景色:とても薄い灰色 */
}

/* Darker background-color on hover */
ul li:hover {	/* :hover 擬似クラス=状態を指定 */
  background: #ccc; /* 背景色:中間の灰色 */
  opacity: 0.7;
}

/* When clicked on, add a background color and strike out text */
ul li.checked { /* jsで，ul liがクリックされるとclass = "checked" にtoggleする */
  background: #888; /*  背景色:濃い灰色 */
  color: #fff; /* 文字の色を白 */
  text-decoration: line-through; /* 文字上に線を引く */
}

/* Add a "checked" mark when clicked on */
ul li.checked::before { /* ::before 擬似要素，直前に要素を追加 */
  content: '';
  position: absolute; /* 絶対座標指定！ */
  border-color: #fff;
  border-style: solid;
  border-width: 0 1px 3px 0;
  top: 10px;
  left: 16px;
  transform: rotate(45deg);
  height: 15px;
  width: 7px;
}

/* Style the close button */
.close { /* class="close" 要素 */
  position: absolute;
  right: 0;
  top: 0;
  padding: 12px 16px 12px 16px;
}

.close:hover {
  background-color: #f44336;
  color: white;
}

/* Style the header */
.header {
  padding: 0 40px 30px 40px;
  text-align: center;
}

/* Clear floats after the header */
.header::after {
  content: "";
  display: table;
  clear: both;
} 

/* Style the input */
input {
  margin: 0;
  border-radius: 0;
  width: 75%;
  height: 44px;
  padding: 10px;
  float: left;
  font-size: 16px;
  border: solid 1px gray;
}

/* Style the "clear Storage" button */
.addBtn {
  padding: 10px;
  width: 25%;
  height: 44px;
  background: #ddd;
  color: #555;
  float: left;
  text-align: center;
  font-size: 16px;
  cursor: pointer;
  transition: 0.3s;
  border-radius: 0;
  border: solid 1px gray;
}

.addBtn:hover {
  background-color: #bbb;
  opacity: 0.7;
}

/* Style the "Add" button */
.clearBtn {
  padding: 10px;
  width: 20%;
  height: 44px;
  background: #559;
  color: #bbb;
  float: left;
  text-align: center;
  font-size: 16px;
  cursor: pointer;
  transition: 0.3s;
  border-radius: 0;
}

.clearBtn:hover {
  background-color: #55f;
}

footer{
  text-align: center;
  margin-top: 40px;
}

footer img{
  width: 900px;
}

footer hr{
  margin-top: 0;
}