:root {  
    --primary-color: #3498db;  
    --secondary-color: #2c3e50;  
    --light-color: #ecf0f1;  
    --dark-color: #34495e;  
    --math-color: #9b59b6;  
    --physics-color: #e74c3c;  
    --subcategory-bg: #f8f9fa;  
    --search-bg: #fff;  
    --delete-color: #e74c3c;  
    --admin-bg: #f8f9fa;  
    --success-color: #2ecc71;  
    --danger-color: #e74c3c;  
    --warning-color: #f39c12;  
    --light-bg: #f8f9fa;  
    --border-color: #ddd;  
    --text-color: #333;  
    --text-light: #777;  
    --box-shadow: 0 3px 15px rgba(0,0,0,0.1);  
    --box-shadow-hover: 0 8px 25px rgba(0,0,0,0.15);  
    --transition-speed: 0.3s;  
    --card-radius: 10px;  
    --btn-radius: 6px;  
}  

* {  
    margin: 0;  
    padding: 0;  
    box-sizing: border-box;  
    font-family: 'Noto Sans JP', 'Helvetica Neue', Arial, sans-serif;  
}  

body {  
    background-color: var(--light-color);  
    color: var(--dark-color);  
    line-height: 1.6;  
    overflow-x: hidden;  
}  

.container {  
    width: 92%;  
    max-width: 1200px;  
    margin: 0 auto;  
}  

/* ヘッダーとナビゲーション */  
header {  
    background-color: var(--secondary-color);  
    color: white;  
    padding: 1.5rem 0;  
    box-shadow: 0 2px 15px rgba(0,0,0,0.15);  
    position: relative;  
    z-index: 100;  
}  

.header-content {  
    display: flex;  
    justify-content: space-between;  
    align-items: center;  
    flex-wrap: wrap;  
    gap: 1rem;  
}  

.logo h1 {  
    font-size: 1.8rem;  
    font-weight: 700;  
    letter-spacing: -0.02em;  
}  

.logo span {  
    display: block;  
    font-size: 1rem;  
    opacity: 0.8;  
    font-weight: 300;  
}  

.nav-container {  
    display: flex;  
    justify-content: space-between;  
    align-items: center;  
    margin-top: 1.2rem;  
    flex-wrap: wrap;  
}  

.nav-links {  
    display: flex;  
    gap: 1.5rem;  
    align-items: center;  
}  

.nav-links a {  
    color: white;  
    text-decoration: none;  
    font-weight: 500;  
    transition: all var(--transition-speed);  
    padding: 0.4rem 0.8rem;  
    border-radius: var(--btn-radius);  
}  

.nav-links a:hover {  
    color: var(--primary-color);  
    background-color: rgba(255, 255, 255, 0.1);  
}  

.nav-links a.active {  
    color: white;  
    background-color: var(--primary-color);  
    border-radius: var(--btn-radius);  
}  

.mobile-menu-toggle {  
    display: none;  
    background: none;  
    border: none;  
    color: white;  
    font-size: 1.5rem;  
    cursor: pointer;  
    transition: transform var(--transition-speed);  
}  

.mobile-menu-toggle:hover {  
    transform: rotate(90deg);  
}  

/* ========== Search Bar (Rev.6 - Maximum Visibility) ========== */  
.search-container{  
    position: relative;  
    width: clamp(240px, 40vw, 460px);  
    margin-left: auto;  
}  

.search-container input{  
    width: 100%;  
    border: 2px solid rgba(55, 100, 190, 0.9);  /* 鮮やかな青の枠線 */  
    background: rgba(255, 255, 255, 0.95);      /* ほぼ白の背景 */  
    border-radius: 9999px;  
    padding: .75rem 3.6rem .75rem 1.25rem;  
    font-size: 1rem;  
    color: #333333;                             /* 濃い黒に近いグレー文字 */  
    outline: none;  
    transition: background .3s, border-color .3s, box-shadow .3s;  
}  

.search-container input::placeholder{  
    color: rgba(70, 70, 70, 0.85);             /* 読みやすい濃いグレー */  
    opacity: 1;  
}  

.search-container input:focus{  
    background: rgba(255, 255, 255, 1);        /* 完全な白 */  
    border-color: #3498db;                     /* 鮮やかなブルー */  
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.35);  
}  
/* フォーカス時に placeholder を非表示に */  
.search-container input:focus::placeholder{  
    opacity: 0;              /* 完全に消す */  
    transition: opacity .15s ease-out;  
}  

/* ブラー時（フォーカスを外したとき）に再表示 */  
.search-container input::placeholder{  
    transition: opacity .15s ease-in;  
}  
/* ---------- Search Button ---------- */  
.search-container .search-btn{  
    position: absolute;  
    top: 50%;  
    right: .45rem;  
    transform: translateY(-50%);  
    width: 2.6rem;  
    height: 2.6rem;  
    border: none;  
    border-radius: 50%;  
    background: #3498db;  
    color: white;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    cursor: pointer;  
    transition: background .3s, transform .3s;  
    z-index: 2;  
}  

.search-container .search-btn:hover{  
    background: #2980b9;  
    transform: translateY(-50%) scale(1.12) rotate(8deg);  
}  

/* クリック時リップル */  
.search-container .search-btn::after{  
    content: '';  
    position: absolute;  
    inset: 0;  
    border-radius: 50%;  
    background: rgba(255,255,255,0.4);  
    transform: scale(.2);  
    opacity: 0;  
    transition: transform .45s, opacity .45s;  
}  

.search-container .search-btn:active::after{  
    transform: scale(1);  
    opacity: 1;  
    transition: 0s;  
}  

/* ---------- Responsive ---------- */  
@media (max-width:768px){  
    .search-container{  
        width: 100%;  
        margin: 0;  
    }  
    .search-container input{  
        font-size: .95rem;  
    }  
}

/* 言語選択 */  
.language-selector {  
    display: flex;  
    gap: 0.5rem;  
    background-color: rgba(255, 255, 255, 0.1);  
    padding: 0.3rem;  
    border-radius: 20px;  
}  

.language-btn {  
    background-color: transparent;  
    border: none;  
    border-radius: 20px;  
    color: white;  
    padding: 0.5rem 1rem;  
    font-size: 0.85rem;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    font-weight: 500;  
}  

.language-btn:hover {  
    background-color: rgba(255, 255, 255, 0.15);  
}  

.language-btn.active {  
    background-color: var(--primary-color);  
    box-shadow: 0 2px 10px rgba(52, 152, 219, 0.3);  
}  

/* ===== 科目ボタン ===== */  
.subject-buttons {  
    display: flex;  
    justify-content: center;  
    gap: 2.5rem;  
    margin: 2.5rem 0;  
    perspective: 1000px;  
}  

.subject-btn {  
    display: flex;  
    flex-direction: column;  
    align-items: center;  
    padding: 2rem 1.5rem;  
    width: 220px;  
    border-radius: 16px;  
    border: none;  
    background-color: white;  
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05), 0 5px 15px rgba(0, 0, 0, 0.05);  
    cursor: pointer;  
    transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);  
    position: relative;  
    overflow: hidden;  
    transform-style: preserve-3d;  
    transform: translateZ(0);  
}  

/* ボタンホバー効果 */  
.subject-btn:hover {  
    transform: translateY(-12px) rotateX(3deg);  
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1), 0 10px 25px rgba(0, 0, 0, 0.1);  
}  

/* アクティブ状態のスタイル改善 */  
.subject-btn.active {  
    background-color: #f9f7fe;  
}  

.subject-btn.math {  
    border-bottom: 5px solid var(--math-color);  
}  

.subject-btn.math.active {  
    box-shadow: 0 10px 25px rgba(155, 89, 182, 0.25);  
    border-bottom-width: 6px;  
}  

.subject-btn.physics {  
    border-bottom: 5px solid var(--physics-color);  
}  

.subject-btn.physics.active {  
    box-shadow: 0 10px 25px rgba(231, 76, 60, 0.25);  
    border-bottom-width: 6px;  
}  

/* アイコンスタイル改善 */  
.subject-icon {  
    font-size: 3rem;  
    margin-bottom: 1.5rem;  
    transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);  
    height: 70px;  
    width: 70px;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    border-radius: 50%;  
    background-color: rgba(255, 255, 255, 0.9);  
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);  
}  

.subject-btn.math .subject-icon {  
    color: var(--math-color);  
    background-color: rgba(155, 89, 182, 0.1);  
}  

.subject-btn.physics .subject-icon {  
    color: var(--physics-color);  
    background-color: rgba(231, 76, 60, 0.1);  
}  

.subject-btn:hover .subject-icon {  
    transform: scale(1.25) translateY(-5px);  
}  

/* テキストスタイル改善 */  
.subject-label {  
    font-weight: 600;  
    font-size: 1.3rem;  
    text-align: center;  
    transition: transform var(--transition-speed);  
}  

.subject-btn:hover .subject-label {  
    transform: scale(1.05);  
}  

/* リップルエフェクト改善 */  
.ripple-effect {  
    position: absolute;  
    border-radius: 50%;  
    background-color: rgba(255, 255, 255, 0.7);  
    animation: ripple 0.8s cubic-bezier(0.25, 0.8, 0.25, 1);  
    pointer-events: none;  
    z-index: 2;  
}  

@keyframes ripple {  
    0% {  
        transform: scale(0);  
        opacity: 0.6;  
    }  
    100% {  
        transform: scale(4);  
        opacity: 0;  
    }  
}  

/* カテゴリーヘッダー */  
.category-header {  
    display: flex;  
    justify-content: space-between;  
    align-items: center;  
    margin: 2.5rem 0 1.2rem;  
    padding: 1rem 1.5rem;  
    border-radius: var(--card-radius);  
    background-color: white;  
    box-shadow: var(--box-shadow);  
}  

.category-header h2 {  
    color: var(--primary-color);  
    font-size: 1.5rem;  
    font-weight: 700;  
    position: relative;  
    padding-left: 1rem;  
}  

.category-header h2::before {  
    content: '';  
    position: absolute;  
    left: 0;  
    top: 0;  
    height: 100%;  
    width: 5px;  
    background-color: var(--primary-color);  
    border-radius: 10px;  
}  

#math-header h2::before, #math-header-en h2::before {  
    background-color: var(--math-color);  
}  

#physics-header h2::before, #physics-header-en h2::before {  
    background-color: var(--physics-color);  
}  

.sort-select {  
    padding: 0.5rem 1rem;  
    border: 1px solid var(--border-color);  
    border-radius: 25px;  
    font-size: 0.9rem;  
    outline: none;  
    cursor: pointer;  
    background-color: white;  
    transition: all var(--transition-speed);  
}  

.sort-select:hover {  
    border-color: var(--primary-color);  
    box-shadow: 0 2px 8px rgba(52, 152, 219, 0.15);  
}  

/* サブカテゴリー */  
.subcategory-container {  
    background-color: white;  
    border-radius: var(--card-radius);  
    padding: 1.2rem;  
    margin-bottom: 2.5rem;  
    box-shadow: var(--box-shadow);  
}  

.subcategory-links {  
    display: flex;  
    flex-wrap: wrap;  
    gap: 0.8rem;  
}  

.subcategory-links a {  
    text-decoration: none;  
    color: var(--dark-color);  
    font-size: 0.95rem;  
    padding: 0.5rem 1rem;  
    border-radius: 25px;  
    transition: all var(--transition-speed);  
    background-color: var(--light-bg);  
}  

.subcategory-links a:hover {  
    background-color: rgba(52, 152, 219, 0.1);  
    color: var(--primary-color);  
    transform: translateY(-2px);  
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.08);  
}  

.subcategory-links a.active {  
    background-color: var(--primary-color);  
    color: white;  
    box-shadow: 0 3px 10px rgba(52, 152, 219, 0.25);  
}  

/* 書籍グリッド */  
.books-grid {  
    display: grid;  
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));  
    gap: 2.5rem;  
    margin-bottom: 3rem;  
}  
/* ===== １行あたりの最大表示数を４冊に制限 ===== */  
@media (min-width: 1200px) {  
    .books-grid {  
      grid-template-columns: repeat(4, 1fr);   /* PC：常に 4 列 */  
    }  
  }  
  
  @media (max-width: 1199px) and (min-width: 768px) {  
    .books-grid {  
      grid-template-columns: repeat(3, 1fr);   /* タブレット：最大 3 列 */  
    }  
  }  
  
  @media (max-width: 767px) and (min-width: 576px) {  
    .books-grid {  
      grid-template-columns: repeat(2, 1fr);   /* 大きめスマホ：最大 2 列 */  
    }  
  }  
  
  @media (max-width: 575px) {  
    .books-grid {  
      grid-template-columns: 1fr;              /* 小さめスマホ：1 列 */  
    }  
  }


.book-card {  
    background-color: white;  
    border-radius: var(--card-radius);  
    overflow: hidden;  
    box-shadow: var(--box-shadow);  
    transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);  
    display: flex;  
    flex-direction: column;  
    position: relative;  
    transform: translateZ(0);  
}  

.book-card:hover {  
    transform: translateY(-10px);  
    box-shadow: var(--box-shadow-hover);  
}  

.book-cover {  
    height: 240px;  
    overflow: hidden;  
    position: relative;  
}  


.book-cover::after {  
    content: '';  
    position: absolute;  
    bottom: 0;  
    left: 0;  
    right: 0;  
    height: 40px;  
    background: linear-gradient(to top, rgba(0,0,0,0.3), transparent);  
}  

.book-cover img {  
    width: 110%;  
    height: 170%;  
    object-fit: cover;  
    transition: transform 0.5s cubic-bezier(0.165, 0.84, 0.44, 1);  
}  

.book-card:hover .book-cover img {  
    transform: scale(1.08);  
}  

.book-info {  
    padding: 1.5rem;  
    flex-grow: 1;  
    display: flex;  
    flex-direction: column;  
    position: relative;  
    z-index: 1;  
}  

.book-title {  
    font-size: 1.15rem;  
    margin-bottom: 0.6rem;  
    line-height: 1.3;  
    font-weight: 600;  
    color: var(--dark-color);  
}  

.book-author {  
    font-size: 0.95rem;  
    color: var(--text-light);  
    margin-bottom: 1rem;  
    font-weight: 400;  
}  

.book-category {  
    display: inline-block;  
    font-size: 0.85rem;  
    padding: 0.3rem 0.8rem;  
    border-radius: 20px;  
    background-color: var(--light-bg);  
    margin-bottom: 1.5rem;  
    font-weight: 500;  
    transition: all var(--transition-speed);  
}  

.book-card:hover .book-category {  
    transform: translateY(-3px);  
    box-shadow: 0 3px 8px rgba(0, 0, 0, 0.05);  
}  

/* サブカテゴリーの色分け */  
.book-category.analysis { background-color: #E8F4FD; color: #2980b9; }  
.book-category.algebra { background-color: #F9EBF9; color: #8e44ad; }  
.book-category.geometry { background-color: #E8F8F5; color: #16a085; }  
.book-category.linear-algebra { background-color: #FEF5E7; color: #d35400; }  
.book-category.calculus { background-color: #FEF9E7; color: #f39c12; }  
.book-category.mechanics { background-color: #F2D7D5; color: #c0392b; }  
.book-category.quantum { background-color: #EAEDED; color: #7f8c8d; }  

.download-btn {  
    display: inline-flex;  
    background-color: var(--primary-color);  
    color: white;  
    padding: 0.8rem 1.2rem;  
    border-radius: var(--btn-radius);  
    text-decoration: none;  
    font-weight: 500;  
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);  
    width: 100%;  
    text-align: center;  
    margin-top: auto;  
    align-items: center;  
    justify-content: center;  
    gap: 0.5rem;  
    position: relative;  
    overflow: hidden;  
    z-index: 1;  
}  

.download-btn::before {  
    content: '';  
    position: absolute;  
    top: 0;  
    left: 0;  
    width: 100%;  
    height: 100%;  
    background-color: rgba(255, 255, 255, 0.1);  
    transform: translateX(-100%);  
    transition: transform 0.3s ease;  
    z-index: -1;  
}  

.download-btn:hover {  
    background-color: #2980b9;  
    transform: translateY(-3px);  
    box-shadow: 0 5px 15px rgba(52, 152, 219, 0.3);  
}  

.download-btn:hover::before {  
    transform: translateX(0);  
}  

/* ページネーション */  
.pagination {  
    display: flex;  
    justify-content: center;  
    align-items: center;  
    margin: 3rem 0 2rem;  
    flex-wrap: wrap;  
    gap: 0.7rem;  
}  

.pagination-btn {  
    background-color: white;  
    border: none;  
    color: var(--dark-color);  
    width: 45px;  
    height: 45px;  
    border-radius: 50%;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    font-weight: 500;  
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.08);  
}  

.pagination-btn:hover {  
    background-color: var(--primary-color);  
    color: white;  
    transform: translateY(-3px);  
    box-shadow: 0 5px 15px rgba(52, 152, 219, 0.25);  
}  

.pagination-btn.active {  
    background-color: var(--primary-color);  
    color: white;  
    box-shadow: 0 5px 15px rgba(52, 152, 219, 0.25);  
}  

.pagination-btn.disabled {  
    opacity: 0.5;  
    cursor: not-allowed;  
    pointer-events: none;  
}  

.pagination-ellipsis {  
    margin: 0 0.3rem;  
    color: var(--text-light);  
}  

/* 検索結果表示 */  
.search-results-header {  
    display: none;  
    justify-content: space-between;  
    align-items: center;  
    margin: 2.5rem 0 1.2rem;  
    padding: 1rem 1.5rem;  
    border-radius: var(--card-radius);  
    background-color: white;  
    box-shadow: var(--box-shadow);  
}  

#clear-search, #clear-search-en {  
    background-color: var(--light-bg);  
    border: none;  
    border-radius: 20px;  
    padding: 0.5rem 1rem;  
    cursor: pointer;  
    font-size: 0.9rem;  
    transition: all var(--transition-speed);  
    display: flex;  
    align-items: center;  
    gap: 0.5rem;  
}  

#clear-search::before, #clear-search-en::before {  
    content: '\f00d';  
    font-family: 'Font Awesome 5 Free';  
    font-weight: 900;  
}  

#clear-search:hover, #clear-search-en:hover {  
    background-color: rgba(231, 76, 60, 0.1);  
    color: var(--danger-color);  
    transform: translateY(-2px);  
}  

/* 管理パネル */  
/* 美化后的管理パネル(admin panel) */  
#admin-panel {  
    display: none;  
    gap: 1.2rem;  
    margin: 2rem 0 1.2rem 0;  
    background: rgba(255,255,255,0.82);  
    padding: 1.5rem 1.2rem 1.2rem 1.2rem;  
    border-radius: 16px;  
    box-shadow: 0 8px 32px rgba(52, 100, 170, 0.10), 0 2px 8px rgba(52,152,219,0.10);  
    flex-wrap: wrap;  
    align-items: flex-start;  
    justify-content: flex-start;  
    border: 1.5px solid var(--primary-color);  
    min-height: 64px;  
    position: relative;  
    overflow: visible;  
    transition: box-shadow 0.3s, background 0.3s;  
}  

#admin-panel::before {  
    content: '';  
    position: absolute;  
    inset: 0;  
    border-radius: 16px;  
    z-index: 0;  
    pointer-events: none;  
    box-shadow: 0 1px 14px rgba(100,120,180,0.07) inset;  
}  

#admin-panel .admin-btn {  
    background: linear-gradient(135deg, #f8fafc 60%, #e9f2fb 100%);  
    border-radius: 8px;  
    box-shadow: 0 2px 8px rgba(52,152,219,0.04);  
    border: 1px solid #eef2fa;  
    color: #29537A;  
    font-size: 1rem;  
    padding: 0.8rem 1.45rem;  
    min-width: 96px;  
    font-weight: 500;  
    align-items: center;  
    gap: 0.6rem;  
    display: flex;  
    transition:   
        background 0.25s,   
        color 0.15s,   
        border 0.2s,   
        box-shadow 0.26s,   
        transform 0.18s;  
    position: relative;  
    z-index: 1;  
}  

#admin-panel .admin-btn:hover, #admin-panel .admin-btn:focus {  
    background: linear-gradient(135deg, #e0efff 40%, #dceaff 100%);  
    color: var(--primary-color);  
    border: 1.5px solid var(--primary-color);  
    box-shadow: 0 8px 24px rgba(52,152,219,0.12), 0 1px 4px rgba(0,0,0,0.06);  
    transform: translateY(-3px) scale(1.05);  
}  

#admin-panel .admin-btn:active {  
    filter: brightness(0.98);  
    transform: scale(0.98);  
}  

#admin-panel .admin-btn i {  
    font-size: 1.1em;  
    opacity: 0.72;  
}

.admin-btn {  
    background-color: rgba(255, 255, 255, 0.9);  
    border: none;  
    border-radius: var(--btn-radius);  
    color: var(--dark-color);  
    padding: 0.6rem 1rem;  
    font-size: 0.95rem;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    display: flex;  
    align-items: center;  
    gap: 0.5rem;  
}  

.admin-btn i {  
    font-size: 0.9rem;  
}  

.admin-btn:hover {  
    background-color: var(--primary-color);  
    color: white;  
    transform: translateY(-2px);  
    box-shadow: 0 3px 10px rgba(52, 152, 219, 0.2);  
}  

/* 削除ボタン */  
.delete-btn {  
    position: absolute;  
    top: 10px;  
    right: 10px;  
    background-color: rgba(231, 76, 60, 0.9);  
    border: none;  
    border-radius: 50%;  
    width: 36px;  
    height: 36px;  
    color: white;  
    font-size: 0.9rem;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    cursor: pointer;  
    opacity: 0;  
    transition: all var(--transition-speed);  
    z-index: 10;  
    transform: translateY(-10px);  
}  

.book-card:hover .delete-btn {  
    opacity: 1;  
    transform: translateY(0);  
}  

.delete-btn:hover {  
    background-color: #c0392b;  
    transform: scale(1.1) !important;  
}  

/* 削除モード時のスタイル */  
.book-card.delete-mode {  
    cursor: pointer;               /* クリック感を強調 */  
    outline: 3px dashed var(--delete-color);
}  

.delete-mode .book-card:hover {  
    transform: scale(1.03) translateY(-5px);  
}  

/* モーダルウィンドウ */  
.modal {  
    display: none;  
    position: fixed;  
    top: 0;  
    left: 0;  
    width: 100%;  
    height: 100%;  
    background-color: rgba(0, 0, 0, 0.75);  
    z-index: 1000;  
    overflow-y: auto;  
    backdrop-filter: blur(5px);  
    -webkit-backdrop-filter: blur(5px);  
}  
.modal.show { display: block; } 

.modal-content {  
    background-color: white;  
    width: 90%;  
    max-width: 800px;  
    margin: 70px auto;  
    border-radius: 15px;  
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);  
    overflow: hidden;  
    transform: translateY(20px);  
    opacity: 0;  
    animation: modalFadeIn 0.4s forwards;  
}  

@keyframes modalFadeIn {  
    to {  
        opacity: 1;  
        transform: translateY(0);  
    }  
}  

.modal-header {  
    padding: 1.8rem;  
    background-color: var(--primary-color);  
    color: white;  
    display: flex;  
    justify-content: space-between;  
    align-items: center;  
}  

.modal-header h2 {  
    font-size: 1.5rem;  
    margin: 0;  
    font-weight: 600;  
}  

.close-modal {  
    font-size: 1.8rem;  
    cursor: pointer;  
    transition: transform var(--transition-speed);  
    width: 35px;  
    height: 35px;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    border-radius: 50%;  
    background-color: rgba(255, 255, 255, 0.1);  
}  

.close-modal:hover {  
    transform: rotate(90deg);  
    background-color: rgba(255, 255, 255, 0.2);  
}  

/* フォームスタイル */  
.form-grid {  
    padding: 1.8rem;  
    display: grid;  
    grid-template-columns: 1fr 1fr;  
    gap: 1.8rem;  
    background-color: white;  
}  

.form-group {  
    display: flex;  
    flex-direction: column;  
}  

.form-group.full-width {  
    grid-column: span 2;  
}  

label {  
    margin-bottom: 0.6rem;  
    font-weight: 500;  
    display: flex;  
    align-items: center;  
    gap: 0.4rem;  
}  

.required {  
    color: var(--danger-color);  
    font-size: 1.2em;  
}  

input[type="text"],  
input[type="number"],  
select,  
textarea {  
    padding: 0.9rem 1rem;  
    border: 1px solid var(--border-color);  
    border-radius: 8px;  
    font-size: 1rem;  
    transition: all var(--transition-speed);  
    background-color: #f9f9f9;  
}  

input[type="text"]:focus,  
input[type="number"]:focus,  
select:focus,  
textarea:focus {  
    outline: none;  
    border-color: var(--primary-color);  
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.15);  
    background-color: white;  
}  

textarea {  
    resize: vertical;  
    min-height: 120px;  
}  

/* ファイルアップロードエリア */  
.upload-area {  
    border: 1px solid var(--border-color);  
    border-radius: 8px;  
    overflow: hidden;  
    background-color: #f9f9f9;  
}  

.upload-area input[type="file"] {  
    display: none;  
}  

.dropzone {  
    border: 2px dashed var(--border-color);  
    border-radius: 8px;  
    padding: 2.5rem;  
    text-align: center;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    background-color: var(--light-bg);  
}  

.dropzone:hover {  
    background-color: rgba(52, 152, 219, 0.05);  
    border-color: var(--primary-color);  
}  

.dropzone.highlight {  
    background-color: rgba(52, 152, 219, 0.1);  
    border-color: var(--primary-color);  
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.15);  
}  

.dropzone i {  
    font-size: 2.5rem;  
    color: var(--primary-color);  
    margin-bottom: 1rem;  
    transition: transform var(--transition-speed);  
}  

.dropzone:hover i {  
    transform: translateY(-5px);  
}  

.dropzone p {  
    margin: 0;  
    color: var(--text-color);  
    font-weight: 500;  
}  

.file-types {  
    margin-top: 0.7rem;  
    font-size: 0.85rem;  
    color: var(--text-light);  
    font-weight: 400;  
}  

.image-preview {  
    display: flex;  
    flex-direction: column;  
    align-items: center;  
    justify-content: center;  
    background-color: var(--light-bg);  
    height: 180px;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    border-radius: 8px;  
}  

.image-preview:hover {  
    background-color: rgba(52, 152, 219, 0.05);  
    border: 2px dashed var(--primary-color);  
}  

.image-preview i {  
    font-size: 3.5rem;  
    color: var(--text-light);  
    margin-bottom: 1rem;  
    transition: transform var(--transition-speed);  
}  

.image-preview:hover i {  
    transform: translateY(-5px);  
    color: var(--primary-color);  
}  

.image-preview img {  
    width: 100%;  
    height: 100%;  
    object-fit: contain;  
    border-radius: 8px;  
}  

.file-preview {  
    display: flex;  
    align-items: center;  
    padding: 1.2rem;  
    background-color: white;  
    border-top: 1px solid var(--border-color);  
}  

.file-icon {  
    font-size: 1.8rem;  
    color: #e74c3c;  
    margin-right: 1.2rem;  
}  

.file-info {  
    flex: 1;  
}  

.file-name {  
    display: block;  
    font-weight: 500;  
    margin-bottom: 0.4rem;  
    color: var(--dark-color);  
}  

.file-size {  
    display: block;  
    font-size: 0.85rem;  
    color: var(--text-light);  
}  

.remove-file {  
    background: none;  
    border: none;  
    width: 32px;  
    height: 32px;  
    border-radius: 50%;  
    display: flex;  
    align-items: center;  
    justify-content: center;  
    color: var(--text-light);  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    background-color: var(--light-bg);  
}  

.remove-file:hover {  
    color: var(--danger-color);  
    background-color: rgba(231, 76, 60, 0.1);  
    transform: rotate(90deg);  
}  

/* モーダルアクション */  
.form-actions {  
    padding: 1.5rem;  
    display: flex;  
    justify-content: flex-end;  
    gap: 1rem;  
    border-top: 1px solid var(--border-color);  
    background-color: var(--light-bg);  
}  

.btn-primary {  
    background-color: var(--primary-color);  
    color: white;  
    border: none;  
    padding: 0.9rem 1.8rem;  
    border-radius: 8px;  
    font-weight: 500;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    display: flex;  
    align-items: center;  
    gap: 0.5rem;  
    position: relative;  
    overflow: hidden;  
}  

.btn-primary::after {  
    content: '';  
    position: absolute;  
    width: 100%;  
    height: 100%;  
    top: 0;  
    left: 0;  
    background-color: rgba(255, 255, 255, 0.1);  
    transform: translateX(-100%);  
    transition: transform 0.3s ease;  
}  

.btn-primary:hover {  
    background-color: #2980b9;  
    transform: translateY(-3px);  
    box-shadow: 0 5px 15px rgba(52, 152, 219, 0.3);  
}  

.btn-primary:hover::after {  
    transform: translateX(0);  
}  

.btn-secondary {  
    background-color: white;  
    color: var(--dark-color);  
    border: 1px solid var(--border-color);  
    padding: 0.9rem 1.8rem;  
    border-radius: 8px;  
    font-weight: 500;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
}  

.btn-secondary:hover {  
    background-color: var(--light-bg);  
    transform: translateY(-3px);  
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);  
}  

.btn-danger {  
    background-color: var(--danger-color);  
    color: white;  
    border: none;  
    padding: 0.9rem 1.8rem;  
    border-radius: 8px;  
    font-weight: 500;  
    cursor: pointer;  
    transition: all var(--transition-speed);  
    display: flex;  
    align-items: center;  
    gap: 0.7rem;  
    position: relative;  
    overflow: hidden;  
}  

.btn-danger::after {  
    content: '';  
    position: absolute;  
    width: 100%;  
    height: 100%;  
    top: 0;  
    left: 0;  
    background-color: rgba(255, 255, 255, 0.1);  
    transform: translateX(-100%);  
    transition: transform 0.3s ease;  
}  

.btn-danger:hover {  
    background-color: #c0392b;  
    transform: translateY(-3px);  
    box-shadow: 0 5px 15px rgba(231, 76, 60, 0.3);  
}  

.btn-danger:hover::after {  
    transform: translateX(0);  
}  

/* 削除確認モーダル */  
.delete-confirm {  
    max-width: 550px;  
}  

.modal-body {  
    padding: 2.5rem 2rem;  
    text-align: center;  
}  

#delete-book-title-ja, #delete-book-title-en {  
    font-weight: 600;  
    color: var(--delete-color);  
}  

.warning {  
    color: var(--danger-color);  
    margin-top: 1.5rem;  
    font-weight: 500;  
    display: flex;  
    justify-content: center;  
    align-items: center;  
    gap: 0.5rem;  
}  

.warning::before {  
    content: '\f071';  
    font-family: 'Font Awesome 5 Free';  
    font-weight: 900;  
}  

.modal-footer {  
    padding: 1.5rem;  
    display: flex;  
    justify-content: center;  
    gap: 1.2rem;  
    border-top: 1px solid var(--border-color);  
    background-color: var(--light-bg);  
}  

/* 結果なしの表示 */  
.no-results {  
    text-align: center;  
    padding: 3rem;  
    background-color: white;  
    border-radius: var(--card-radius);  
    box-shadow: var(--box-shadow);  
    margin: 2rem 0;  
    color: var(--text-light);  
    font-size: 1.2rem;  
    position: relative;  
}  

.no-results::before {  
    content: '\f002';  
    font-family: 'Font Awesome 5 Free';  
    font-weight: 900;  
    font-size: 3rem;  
    display: block;  
    margin-bottom: 1rem;  
    color: var(--text-light);  
    opacity: 0.5;  
}  

/* フッター */  
footer {  
    background-color: var(--secondary-color);  
    color: white;  
    padding: 2.5rem 0;  
    margin-top: 5rem;  
    position: relative;  
}  

footer::before {  
    content: '';  
    position: absolute;  
    top: -20px;  
    left: 0;  
    width: 100%;  
    height: 20px;  
    background: linear-gradient(to top right, transparent 49%, var(--secondary-color) 50%),  
                linear-gradient(to top left, transparent 49%, var(--secondary-color) 50%);  
    background-size: 50px 20px;  
}  

.footer-content {  
    display: flex;  
    justify-content: center;  
    align-items: center;  
    flex-direction: column;  
}  

.copyright {  
    font-size: 0.95rem;  
    opacity: 0.8;  
    text-align: center;  
    line-height: 1.6;  
}  

/* 言語切り替え */  
.ja, .en {  
    display: none;  
}  

/* No-JS ノートの追加 */  
.no-js-note {  
    background-color: rgba(243, 156, 18, 0.1);  
    border-left: 4px solid var(--warning-color);  
    padding: 1rem;  
    margin: 1rem 0;  
    display: none;  
}  

body:not(:has(script)) .no-js-note {  
    display: block;  
}  

/* レスポンシブデザイン */  
@media (max-width: 992px) {  
    .books-grid {  
        grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));  
        gap: 1.5rem;  
    }  
    
    .subject-buttons {  
        gap: 1.5rem;  
    }  
    
    .subject-btn {  
        width: 180px;  
        padding: 1.5rem 1rem;  
    }  
}  



@media (max-width: 576px) {  
    .subject-buttons {  
        flex-direction: column;  
        align-items: center;  
        gap: 1rem;  
        margin: 1.5rem 0;  
    }  
    
    .subject-btn {  
        width: 90%;  
        max-width: 280px;  
    }  
    
    .books-grid {  
        grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));  
        gap: 1rem;  
    }  

    .book-cover {  
        height: 180px;  
    }  

    .book-title {  
        font-size: 1rem;  
    }  
    
    .book-info {  
        padding: 1rem;  
    }  
    
    .pagination {  
        gap: 0.4rem;  
    }  
    
    .pagination-btn {  
        width: 38px;  
        height: 38px;  
    }  
    
    .modal-content {  
        margin: 40px auto;  
    }  
    
    .modal-header {  
        padding: 1.2rem;  
    }  
    
    .modal-body {  
        padding: 1.5rem 1rem;  
    }  
    
    .dropzone {  
        padding: 1.5rem 1rem;  
    }  
}  

/* 印刷用スタイル */  
@media print {  
    header, footer, .nav-container, .search-container,   
    .language-selector, .subcategory-container, .pagination,  
    .download-btn, #admin-buttons, #admin-panel {  
        display: none !important;  
    }  
    
    body {  
        background-color: white;  
    }  
    
    .container {  
        width: 100%;  
        max-width: none;  
    }  
    
    .books-grid {  
        grid-template-columns: repeat(3, 1fr);  
        gap: 2rem;  
    }  
    
    .book-card {  
        break-inside: avoid;  
        page-break-inside: avoid;  
        box-shadow: none;  
        border: 1px solid #eee;  
    }  
}



.admin-btn.delete-active {  
    background-color: var(--danger-color);  
    color: #fff;  
    box-shadow: 0 2px 14px rgba(231, 76, 60, 0.25);  
    border: 2px solid var(--danger-color);  
    font-weight: bold;  
}

/* 特定按钮日文横排 */  
.horizontal-ja,  
.horizontal-ja .ja {  
    writing-mode: horizontal-tb !important;  
    text-orientation: initial !important;  
    display: inline;  
}

/* 让管理员入口图标更小、更隐秘 */  
.admin-entry-btn {  
    background: transparent;  
    border: none;  
    box-shadow: none;  
    padding: 4px;  
    margin: 0 4px;  
}  

.admin-entry-btn .admin-icon {  
    font-size: 1em !important;           /* 明显缩小图标 */  
    opacity: 0.23 !important;            /* 更隐约 */  
    filter: grayscale(95%) blur(0.5px);  /* 几乎全灰+微模糊 */  
    transition: opacity 0.2s, filter 0.2s;  
    color: #888 !important;              /* 更灰色（防某些主题彩色覆盖） */  
    vertical-align: baseline;  
    pointer-events: auto;  
}  

/* 悬停时稍稍显眼一点 */  
.admin-entry-btn:hover .admin-icon,  
.admin-entry-btn:focus .admin-icon {  
    opacity: 0.55 !important;  
    filter: none !important;  
    color: #444 !important;  
}

/* 管理员登录modal美化 */  
#admin-login-modal {  
    display: none;  
    position: fixed; z-index: 9999; left: 0; top: 0;  
    width: 100vw; height: 100vh;  
    background: rgba(40,58,90,0.18);  
    align-items: center; justify-content: center;  
  }  
  #admin-login-modal.show { display: flex; }  
  
  .admin-login-content {  
    background: #fff;  
    border-radius: 20px;  
    box-shadow: 0 8px 40px rgba(44,62,80,0.16), 0 1.5px 6px rgba(90,100,140,0.09);  
    width: 98vw; max-width: 360px; min-height: 380px;  
    padding: 2.1rem 2.2rem 2.1rem 2.2rem;  
    display: flex; flex-direction: column; align-items: center;  
    animation: fadeInPop 0.34s cubic-bezier(.6,.05,.6,.97);  
    position: relative;  
  }  
  
  @keyframes fadeInPop {  
    0% { opacity: 0; transform: scale(0.9);}  
    100% { opacity: 1; transform: scale(1);}  
  }  
  #admin-btn {  
    cursor: pointer;  
    transition: transform 0.2s;  
  }  
  
  #admin-btn:active {  
    transform: scale(0.95);  
  }
  
  .admin-login-logo-wrap {  
    margin-bottom: 10px;  
  }  
  .admin-login-logo {  
    width: 64px; height: 64px; border-radius: 10px; background: #f7f8fc;  
    box-shadow: 0 1px 6px rgba(75,100,200,0.12);  
    display: block; object-fit: contain;  
  }  
  
  .admin-login-title {  
    margin: 10px 0 6px 0;  
    text-align: center; font-size: 1.25rem; color: #245490;  
    font-weight: 700; letter-spacing: 1.5px;  
  }  
  
  .admin-login-desc {  
    font-size: 1em; margin-bottom: 20px; color: #888; text-align: center;  
  }  
  
  .admin-login-input {  
    border-radius: 8px;  
    border: 1.5px solid #bcd4f1;  
    padding: 0.75em 1em; width: 100%;  
    margin-bottom: 20px;  
    font-size: 1.08em;  
    transition: border 0.2s;  
    outline: none;  
  }  
  .admin-login-input:focus {  
    border-color: #3d7aff;  
  }  
  
  .admin-login-btn-row {  
    display: flex; gap: 16px; width: 100%; justify-content: center;  
  }  
  .admin-login-ok {  
    background: linear-gradient(90deg,#528ff2,#75c9fa 100%);  
    color: #fff;  
    font-weight: 600;  
    border: none;  
    padding: 0.6em 1.6em;  
    border-radius: 8px;  
    cursor: pointer;  
    box-shadow: 0 1.5px 4px rgba(85,140,200,0.13);  
  }  
  .admin-login-ok:hover { filter: brightness(1.13);}  
  
  .admin-login-cancel {  
    background: #e6ebf5; color: #5472af; font-weight: 500;  
    border: none;  
    padding: 0.6em 1.3em;  
    border-radius: 8px;  
    cursor: pointer;  
  }  
  .admin-login-cancel:hover { background: #f2f4f9; }  
  
  .admin-login-error {  
    min-height: 1.5em;  
    color: #e04753; font-size: 0.98em;  
    margin-top: 10px; text-align: center;  
    font-weight: 500; letter-spacing: 1px;  
  }
  /* 增强下载按钮样式 */
.download-btn {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--primary-color);
    color: white;
    padding: 0.8rem 1.2rem;
    border-radius: 4px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    width: 100%;
    text-align: center;
    margin-top: auto;
    box-shadow: 0 4px 10px rgba(52, 152, 219, 0.3);
    font-size: 1.05rem;
}

.download-btn:hover {
    background-color: #2980b9;
    transform: translateY(-2px);
    box-shadow: 0 6px 15px rgba(52, 152, 219, 0.4);
}

.download-btn i {
    margin-right: 8px;
    font-size: 1.1rem;
}

/* 文件夹浏览按钮 */
.folder-btn {
    display: inline-block;
    background-color: var(--secondary-color);
    color: white;
    padding: 0.7rem 1.2rem;
    border-radius: 4px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    text-align: center;
    margin-left: 1rem;
    box-shadow: 0 4px 10px rgba(44, 62, 80, 0.2);
}

.folder-btn:hover {
    background-color: #3d5871;
    transform: translateY(-2px);
    box-shadow: 0 6px 15px rgba(44, 62, 80, 0.3);
}

.folder-btn i {
    margin-right: 6px;
}

/* 分类文件夹按钮 */
.category-folder-btn {
    display: inline-flex;
    align-items: center;
    background-color: var(--light-color);
    color: var(--dark-color);
    padding: 0.5rem 1rem;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    margin-left: 1rem;
    border: 1px solid #ddd;
}

.category-folder-btn:hover {
    background-color: #ddd;
}

.category-folder-btn i {
    margin-right: 6px;
    color: var(--primary-color);
}

/* 书籍卡片悬停时强调下载按钮 */
.book-card:hover .download-btn {
    background-color: #2980b9;
    transform: translateY(-2px);
}

/* 已有其他子类别颜色 */
.book-category.analysis { background-color: #E8F4FD; color: #2980b9; }  
.book-category.algebra { background-color: #F9EBF9; color: #8e44ad; }  
.book-category.geometry { background-color: #E8F8F5; color: #16a085; }  
.book-category.linear-algebra { background-color: #FEF5E7; color: #d35400; }  
.book-category.calculus { background-color: #FEF9E7; color: #f39c12; }  
.book-category.mechanics { background-color: #F2D7D5; color: #c0392b; }  
.book-category.quantum { background-color: #EAEDED; color: #7f8c8d; }

/* 新增你要求的分类颜色 */
.book-category.statistics {
    background-color: #dbeeff; 
    color: #1e90ff;
}

.book-category.differential-equations {
    background-color: #ffe6cc; 
    color: #d2691e;
}

.book-category.stochastic-differential-equations {
    background-color: #e6ffe6; 
    color: #2e8b57;
}

.book-category.topology {
    background-color: #f0e6ff; 
    color: #6a0dad;
}

.book-category.differential-geometry {
    background-color: #fff0f5; 
    color: #c71585;
}

.book-category.algebraic-geometry {
    background-color: #f9f9f9; 
    color: #4682b4;
}