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                <a href="#" class="btn">Nice Button</a>


- 文字サイズ:22px
- 背景色:#0bd
- 文字色:白
- ボタンの内側の余白:上下10px、左右20px
- 角丸:5px
- リンクテキストの下線を消去
- ボタンを画面左右中央に表示
body {
  padding: 20px;
  text-align: center;

.btn {
  font-size: 22px;
  background: #0bd;
  color: #fff;
  padding: 10px 20px;
  border-radius: 5px;
  text-decoration: none;

/* ボタンにカーソルを合わせると背景色を#0bbに変更 */
.btn:hover {
  background: #0bb;

/* 画面幅が400px以下になるとボタンの幅を画面いっぱいに表示 */
@media (max-width: 400px){
  .btn {
    display: block;