* {
    box-sizing: border-box;
    font-family: serif;
 }

body {
    min-height: 150vh;
    margin: 0;
    padding: 0;
    background-color: rgb(230, 230, 230);
}

header {
    width: 100%;
    padding: 30px 4% 10px;
    background-color: #fff;
    position: sticky;
    top: 0;
    display: flex;
    align-items: center;
}

h1 {
    margin: 0; padding: 0;
    /*フォントのサイズは適当なものを決める*/
    font-size: 25px;
 }

 a {	
    text-decoration: none;
    color: #4b4b4b;
 }

 nav a:hover {
    background-color: skyblue;
 }

 ul {
    list-style: none;
    margin: 0;
    display: flex;
 }

 li {
    margin: 0 0 0 15px;
    font-size: 17px;
 }

 nav {
    margin: 0 0 0 auto;
 }

 h2 {
    font-size: 1.2em;
    color: #4e4e4e;/*文字色*/
    border: solid 3px #4e4e4e;/*線色*/
    padding: 0.5em;/*文字周りの余白*/
    border-radius: 0.5em;/*角丸*/
  }

  .main {
    margin-left: auto;
    margin-right: auto;
    width: 600px;
    
  }

  .main img {
   margin: 10px;
   border-radius: 0.5em;/*角丸*/
  }