/* 全体のスタイル */
body {
    font-family: 'Helvetica Neue', Arial, 'Hiragino Kaku Gothic ProN', 'Hiragino Sans', Meiryo, sans-serif;
    line-height: 1.8;
    color: #333;
    background-color: #f9f9f9;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 20px;
    background-color: #fff;
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.05);
    border-radius: 8px;
}

/* ヘッダーとナビゲーション */
header {
    background-color: #005f73;
    color: #fff;
    padding: 20px;
    text-align: center;
    border-radius: 8px 8px 0 0;
}

header h1 {
    margin: 0;
    font-size: 2.5em;
    font-weight: bold;
}

nav {
    background-color: #0a9396;
    padding: 10px 0;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
}

nav li {
    margin: 0 15px;
}

nav a {
    color: #fff;
    text-decoration: none;
    font-weight: bold;
    padding: 5px 10px;
    border-radius: 4px;
    transition: background-color 0.3s;
}

nav a:hover, nav a.active {
    background-color: #94d2bd;
}


/* メインコンテンツ */
main {
    padding: 30px 20px;
}

section {
    margin-bottom: 40px;
    border-bottom: 1px solid #e0e0e0;
    padding-bottom: 30px;
}

section:last-child {
    border-bottom: none;
    margin-bottom: 0;
}

h2 {
    font-size: 2em;
    color: #005f73;
    border-left: 5px solid #0a9396;
    padding-left: 15px;
    margin-bottom: 25px;
}

h3 {
    font-size: 1.7em;
    color: #0a9396;
    margin-top: 40px;
    margin-bottom: 20px;
    border-bottom: 2px solid #94d2bd;
    padding-bottom: 10px;
}

h4 {
    font-size: 1.4em;
    color: #005f73;
    margin-top: 30px;
    margin-bottom: 15px;
    border-bottom: 1px dashed #94d2bd;
    padding-bottom: 5px;
}

h5 {
    font-size: 1.2em;
    color: #333;
    margin-top: 25px;
    margin-bottom: 10px;
    font-weight: bold;
}

p, li {
    font-size: 1em;
}

/* リストのスタイル */
ul, ol {
    padding-left: 20px;
}

ul > li {
    list-style-type: disc;
    margin-bottom: 10px;
}

ol > li {
    margin-bottom: 10px;
}

/* テーブルのスタイル */
table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
    font-size: 0.9em;
}

th, td {
    border: 1px solid #ddd;
    padding: 12px;
    text-align: left;
    vertical-align: top;
}

thead th {
    background-color: #0a9396;
    color: #fff;
    font-weight: bold;
}

tbody tr:nth-child(even) {
    background-color: #f2f2f2;
}

tbody .part-header td {
    background-color: #e9d8a6;
    font-weight: bold;
    text-align: center;
}

/* 強調テキスト */
strong, b {
    color: #d62828;
    font-weight: bold;
}

/* 課題セクション */
.assignment-box {
    border: 2px solid #94d2bd;
    background-color: #e8f7f3;
    padding: 20px;
    margin-top: 30px;
    border-radius: 8px;
}

.assignment-box h3 {
    margin-top: 0;
    color: #005f73;
    border-bottom: none;
}


/* 講義ページ用タブUI */
.tab-nav {
    display: flex;
    border-bottom: 2px solid #0a9396;
    margin-bottom: 30px;
}

.tab-nav-item {
    padding: 10px 25px;
    cursor: pointer;
    background-color: #f2f2f2;
    color: #333;
    border: 1px solid #ddd;
    border-bottom: none;
    border-radius: 8px 8px 0 0;
    margin-right: 5px;
    font-weight: bold;
    transition: all 0.3s;
}

.tab-nav-item.active {
    background-color: #0a9396;
    color: #fff;
    border-color: #0a9396;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.lecture-img {
    max-width: 100%;
    height: auto;
    margin: 20px 0;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

/* DXレポートページ用スタイル */
.report-title {
    font-size: 2.2em;
    text-align: center;
    color: #005f73;
    margin-bottom: 30px;
    border-bottom: 2px solid #0a9396;
    padding-bottom: 15px;
}

.toc {
    background-color: #e8f7f3;
    border: 1px solid #94d2bd;
    padding: 20px 25px;
    margin-bottom: 40px;
    border-radius: 8px;
}

.toc h3 {
    margin-top: 0;
    border-bottom: none;
    color: #005f73;
}

.toc ul {
    list-style: none;
    padding-left: 0;
}

.toc ul li {
    margin-bottom: 8px;
}

.toc ul li a {
    text-decoration: none;
    color: #333;
    transition: color 0.3s;
}

.toc ul li a:hover {
    color: #0a9396;
}

.toc ul ul {
    padding-left: 20px;
    margin-top: 8px;
}

blockquote {
    border-left: 4px solid #94d2bd;
    padding-left: 20px;
    margin: 20px 0;
    font-style: italic;
    color: #555;
    background-color: #f9f9f9;
}

.references-list {
    list-style-type: decimal;
    padding-left: 25px;
    font-size: 0.9em;
}

.references-list li {
    margin-bottom: 12px;
}

.references-list li a {
    color: #005f73;
    text-decoration: none;
}

.references-list li a:hover {
    text-decoration: underline;
}

/* フッター */
footer {
    text-align: center;
    padding: 20px;
    margin-top: 30px;
    font-size: 0.9em;
    color: #777;
}

/* クイズ・ケーススタディ用スタイル */
.quiz-box {
    background-color: #fcf8e3;
    border: 2px solid #f0ad4e;
    border-radius: 8px;
    padding: 20px;
    margin: 30px 0;
}

.quiz-box .question {
    font-size: 1.1em;
    color: #8a6d3b;
    margin-bottom: 15px;
}

.quiz-box .answer {
    background-color: #fff;
    border: 1px dashed #f0ad4e;
    padding: 15px;
    border-radius: 6px;
}