header {
    width: 100%;
    min-height: 23px;
    display:flex;
    flex-direction: row;
    flex-wrap: wrap;
    background-color: #1d376e;
    color: white;
    padding:5px;
    padding-left: 0;
    margin-bottom: 5px;
    align-content: center;
    align-items: center;
}

header a {
    color: white;
    text-decoration: none;
    margin-left: 20px;
}

body {
    margin-top: 0px;
    margin-bottom: 0px;
    padding: 0px;
    background-color: #cecece;
}

hr {
    height: 0px;
    color: black;
    border: 1px solid black;
}

main {
    padding:9px;
    color: black;
}
.page {
    background-color: white;
    min-height: 100vh;
}

.page h2 {
    background-color: #1d376e;
    color: white;
    padding:5px;
}

.page h3 {
    background-color: #1d376e;
    color: white;
    padding:5px;
}

html {
  scroll-behavior: smooth;
}

@media screen and (min-width: 600px) {
    body {
        margin-left: 6%;
        margin-right: 6%;
    }
}

@media screen and (max-width: 599px) {
    body {
        margin-left: 0px;
        margin-right: 0px;
    }

    header {
        position: fixed;
    }

    main {
        padding-top: 115px;
    }
}

pre {
    background-color: #d8d8d8;
    border-left: #ccc 9px solid;
    padding:10px;
    text-overflow: clip;
    word-wrap: break-word;
    text-wrap:inherit;
    white-space: pre-wrap;       /* 改行保持＋折り返し */
}