/* --- 基本設定 --- */
:root {
    --bg-color: #fdfdfd;
    --text-color: #333333;
    --accent-color: #2E8B57;
    /* SeaGreen */
    --accent-hover-color: #257247;
    --border-color: #eeeeee;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Serif JP', serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.8;
    margin: 0;
    padding: 0;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* --- レイアウト --- */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

header,
section,
footer {
    padding: 80px 0;
}

section {
    border-bottom: 1px solid var(--border-color);
}

.ads-section,
footer {
    border-bottom: none;
}

/* --- タイポグラフィ --- */
h1,
h2,
h3 {
    font-weight: 700;
    line-height: 1.4;
    margin-top: 0;
}

h1 {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 1rem;
}

.subtitle {
    font-size: 1.1rem;
    text-align: center;
    color: #555;
}

h2 {
    font-size: 2rem;
    color: var(--accent-color);
    text-align: center;
    margin-bottom: 40px;
}

p {
    margin-bottom: 1em;
}

/* --- コンポーネント --- */
.book-title {
    font-weight: bold;
    display: block;
    text-align: center;
    margin: 30px 0;
    font-size: 1.2rem;
}

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

.features-list li {
    margin-bottom: 30px;
}

.features-list h3 {
    font-size: 1.3rem;
    margin-bottom: 10px;
    position: relative;
    padding-left: 25px;
}

.features-list h3::before {
    content: '・';
    color: var(--accent-color);
    position: absolute;
    left: 0;
    font-weight: bold;
}

.testimonial {
    background-color: #ffffff;
    border-left: 4px solid var(--accent-color);
    padding: 20px 30px;
    margin-bottom: 30px;
}

.testimonial-cite {
    display: block;
    text-align: right;
    margin-top: 15px;
    font-style: normal;
}

.cta-section {
    text-align: center;
}

.cta-button {
    display: inline-block;
    background-color: var(--accent-color);
    color: #ffffff;
    text-decoration: none;
    padding: 15px 40px;
    border-radius: 5px;
    font-size: 1.2rem;
    font-weight: bold;
    transition: background-color 0.3s ease, transform 0.3s ease;
}

.cta-button:hover,
.cta-button:focus {
    background-color: var(--accent-hover-color);
    transform: translateY(-2px);
    color: #ffffff;
}

.final-message {
    margin-top: 20px;
    font-style: italic;
    color: #555;
}

/* --- アニメーション --- */
.fade-in-section {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}

.fade-in-section.is-visible {
    opacity: 1;
    transform: translateY(0);
}

/* --- トップへ戻るボタン --- */
#back-to-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
    display: none;
    width: 50px;
    height: 50px;
    background-color: var(--accent-color);
    color: #ffffff;
    text-decoration: none;
    text-align: center;
    line-height: 50px;
    font-size: 20px;
    border-radius: 50%;
    opacity: 0.7;
    transition: opacity 0.3s ease;
}

#back-to-top:hover {
    opacity: 1;
}

/* ヘッダーバナー */
.header-banner {
    width: 100%;
    height: auto;
    margin-bottom: 2rem;
    /* 見出しとの間隔 */
    border-radius: 8px;
}

/* 本の紹介セクション */
.book-introduction {
    text-align: center;
    /* 画像やタイトルを中央揃えに */
}

/* 本のカバー画像 */
.book-cover {
    max-width: 300px;
    /* 表示サイズを調整 */
    width: 100%;
    height: auto;
    margin: 1rem auto 2rem;
    /* 上下の間隔 */
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.2);
    /* 影をつけて立体感を出す */
}

.language-switcher {
    text-align: center;
    padding: 1em 0;
    background-color: #fff;
    border-bottom: 1px solid #eee;
}

.language-switcher a {
    margin: 0 0.7em;
    text-decoration: none;
    color: #555;
    font-weight: normal;
    font-size: 1em;
    transition: color 0.3s;
}

.language-switcher a:hover,
.language-switcher a.active {
    color: #d33a2c;
    text-decoration: none;
}

.language-switcher a.active {
    font-weight: bold;
}

.cta-button {
    margin: 10px auto;
}

/* --- レスポンシブ対応 --- */
@media (max-width: 768px) {

    header,
    section,
    footer {
        padding: 60px 0;
    }

    h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.6rem;
    }
}