:root {
    /* カラーシステム - より洗練されたトーン */
    --color-bg: #fafafa;
    --color-surface: #ffffff;
    --color-text-primary: #1a1a1a;
    --color-text-secondary: #6b6b6b;
    --color-text-tertiary: #9e9e9e;
    --color-border: #e8e8e8;
    --color-border-subtle: #f0f0f0;
    
    /* アクセントカラー - 控えめで上品に */
    --color-palpation: #d32f2f;
    --color-palpation-light: #ffebee;
    --color-ortho: #1976d2;
    --color-ortho-light: #e3f2fd;
    
    /* インタラクション */
    --color-hover: #f5f5f5;
    --color-active: #eeeeee;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
    
    /* タイポグラフィ - システムフォント最適化 */
    --font-base: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Yu Gothic", Meiryo, sans-serif;
    --font-display: "Hiragino Sans", -apple-system, sans-serif;
    
    /* スペーシングシステム - 8pxグリッド */
    --space-1: 0.5rem;   /* 8px */
    --space-2: 1rem;     /* 16px */
    --space-3: 1.5rem;   /* 24px */
    --space-4: 2rem;     /* 32px */
    --space-5: 2.5rem;   /* 40px */
    --space-6: 3rem;     /* 48px */
    --space-8: 4rem;     /* 64px */
    
    /* ボーダーラディウス */
    --radius-xs: 4px;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    
    /* トランジション */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-base);
    background: var(--color-bg);
    color: var(--color-text-primary);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    font-size: 16px;
    letter-spacing: -0.01em;
}

/* ============================================
   ヘッダー - よりミニマルに
   ============================================ */
.app-header {
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border-subtle);
    padding: var(--space-3) var(--space-4);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
    background: rgba(255, 255, 255, 0.95);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.logo {
    height: 28px;
    width: auto;
    opacity: 0.9;
}

.app-header h1 {
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--color-text-primary);
    letter-spacing: -0.02em;
    font-family: var(--font-display);
}

/* ============================================
   メイン
   ============================================ */
.app-main {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--space-4) var(--space-3);
    min-height: calc(100vh - 180px);
}

@media (min-width: 768px) {
    .app-main {
        padding: var(--space-6) var(--space-4);
    }
}

/* 読み込み中 */
.loading-screen {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 60vh;
    color: var(--color-text-tertiary);
}

.spinner {
    width: 40px;
    height: 40px;
    border: 2px solid var(--color-border);
    border-top-color: var(--color-text-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.loading-screen p {
    margin-top: var(--space-3);
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

/* スクリーン共通 */
.screen {
    animation: fadeInUp 0.4s var(--transition-base);
}

@keyframes fadeInUp {
    from { 
        opacity: 0; 
        transform: translateY(16px);
    }
    to { 
        opacity: 1; 
        transform: translateY(0);
    }
}

.screen-title {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--space-5);
    color: var(--color-text-primary);
    letter-spacing: -0.03em;
    font-family: var(--font-display);
}

.screen-header {
    margin-bottom: var(--space-4);
}

/* 戻るボタン */
.btn-back {
    background: none;
    border: none;
    color: var(--color-text-secondary);
    font-size: 0.9375rem;
    cursor: pointer;
    padding: var(--space-1) 0;
    margin-bottom: var(--space-2);
    transition: color var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: var(--space-1);
    font-weight: 400;
}

.btn-back:hover {
    color: var(--color-text-primary);
}

.btn-back:active {
    transform: translateX(-2px);
}

/* ============================================
   カテゴリー選択 - エレガントで触りやすく
   ============================================ */
.category-buttons {
    display: grid;
    gap: var(--space-3);
    margin-top: var(--space-6);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.btn-category {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-6) var(--space-4);
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-surface);
    cursor: pointer;
    transition: all var(--transition-base);
    min-height: 160px;
    position: relative;
    overflow: hidden;
}

/* カテゴリーボタンの背景画像 */
.btn-category::after {
    content: '';
    position: absolute;
    inset: 0;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    opacity: 0.20;
    transition: opacity var(--transition-base);
    z-index: 0;
}

.btn-palpation::after {
    background-image: url('../assets/category/palpation-bg.jpg');
}

.btn-ortho::after {
    background-image: url('../assets/category/ortho-bg.jpg');
}

.btn-category::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, transparent 0%, transparent 100%);
    opacity: 0;
    transition: opacity var(--transition-base);
    z-index: 1;
}

.btn-category:hover::after {
    opacity: 0.35;
}

.btn-category:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: transparent;
}

.btn-category:hover::before {
    opacity: 1;
}

.btn-category:active {
    transform: translateY(-2px);
}

.btn-palpation {
    border-color: var(--color-palpation);
}

.btn-palpation::before {
    background: linear-gradient(135deg, var(--color-palpation-light) 0%, transparent 100%);
}

.btn-palpation:hover {
    border-color: var(--color-palpation);
    box-shadow: 0 8px 32px rgba(211, 47, 47, 0.15);
}

.btn-ortho {
    border-color: var(--color-ortho);
}

.btn-ortho::before {
    background: linear-gradient(135deg, var(--color-ortho-light) 0%, transparent 100%);
}

.btn-ortho:hover {
    border-color: var(--color-ortho);
    box-shadow: 0 8px 32px rgba(25, 118, 210, 0.15);
}

.category-label {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--space-1);
    letter-spacing: -0.02em;
    position: relative;
    z-index: 2;
    text-shadow: 
        0 0 15px rgba(255, 255, 255, 0.95),
        0 0 25px rgba(255, 255, 255, 0.8),
        0 2px 6px rgba(0, 0, 0, 0.15);
}

.btn-palpation .category-label {
    color: var(--color-palpation);
}

.btn-ortho .category-label {
    color: var(--color-ortho);
}

.category-sub {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    font-weight: 600;
    letter-spacing: 0.02em;
    position: relative;
    z-index: 2;
    text-shadow: 
        0 0 12px rgba(255, 255, 255, 0.95),
        0 0 20px rgba(255, 255, 255, 0.8),
        0 1px 4px rgba(0, 0, 0, 0.15);
}

@media (min-width: 640px) {
    .category-buttons {
        grid-template-columns: repeat(2, 1fr);
        max-width: 800px;
    }
}

/* ============================================
   部位選択 - グリッドの美しさ（解剖図の透かし付き）
   ============================================ */
.body-part-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: var(--space-2);
}

.body-part-card {
    padding: var(--space-4);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    cursor: pointer;
    transition: all var(--transition-base);
    text-align: center;
    min-height: 110px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

/* 解剖図の透かし（実際の理学療法の写真を使用） */
.body-part-card::after {
    content: '';
    position: absolute;
    inset: 0;
    opacity: 0.10;
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    transition: all var(--transition-base);
    pointer-events: none;
    filter: grayscale(70%) brightness(1.3);
    border-radius: var(--radius-md);
}

/* 各部位の写真 - 触診用 */
.body-part-card[data-category="palpation"][data-body-part="head-neck"]::after {
    background-image: url('../assets/palpation/head-neck.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="shoulder"]::after {
    background-image: url('../assets/palpation/shoulder.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="elbow"]::after {
    background-image: url('../assets/palpation/elbow.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="wrist"]::after {
    background-image: url('../assets/palpation/wrist.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="trunk"]::after {
    background-image: url('../assets/palpation/trunk.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="hip"]::after {
    background-image: url('../assets/palpation/hip.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="knee"]::after {
    background-image: url('../assets/palpation/knee.jpg?v=2');
}

.body-part-card[data-category="palpation"][data-body-part="ankle"]::after {
    background-image: url('../assets/palpation/ankle.jpg?v=2');
}

/* 各部位の写真 - 整形外科的テスト用 */
.body-part-card[data-category="ortho"][data-body-part="head-neck"]::after {
    background-image: url('../assets/anatomy/head-neck.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="shoulder"]::after {
    background-image: url('../assets/anatomy/shoulder.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="elbow"]::after {
    background-image: url('../assets/anatomy/elbow.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="wrist"]::after {
    background-image: url('../assets/anatomy/wrist.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="trunk"]::after {
    background-image: url('../assets/anatomy/trunk.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="hip"]::after {
    background-image: url('../assets/anatomy/hip.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="knee"]::after {
    background-image: url('../assets/anatomy/knee.jpg');
}

.body-part-card[data-category="ortho"][data-body-part="ankle"]::after {
    background-image: url('../assets/anatomy/ankle.jpg');
}

.body-part-card::before {
    content: '';
    position: absolute;
    inset: -1px;
    border-radius: var(--radius-md);
    padding: 1px;
    background: linear-gradient(135deg, var(--color-text-primary), transparent);
    -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
    opacity: 0;
    transition: opacity var(--transition-base);
}

.body-part-card:hover:not(.disabled) {
    background: var(--color-hover);
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.body-part-card:hover:not(.disabled)::before {
    opacity: 1;
}

.body-part-card:hover:not(.disabled)::after {
    opacity: 0.22;
    transform: scale(1.05);
}

.body-part-card.disabled {
    opacity: 0.35;
    cursor: not-allowed;
    background: var(--color-bg);
}

.body-part-card.disabled::after {
    opacity: 0.05;
}

.body-part-name {
    font-size: 1rem;
    font-weight: 700;
    color: var(--color-text-primary);
    letter-spacing: -0.01em;
    position: relative;
    z-index: 1;
    text-shadow: 
        0 0 10px rgba(255, 255, 255, 1),
        0 0 20px rgba(255, 255, 255, 0.9),
        0 0 30px rgba(255, 255, 255, 0.8),
        0 2px 4px rgba(0, 0, 0, 0.2);
}

.body-part-card.disabled .body-part-name::after {
    content: " (準備中)";
    font-size: 0.75rem;
    display: block;
    margin-top: var(--space-1);
    font-weight: 400;
    color: var(--color-text-tertiary);
}

@media (min-width: 640px) {
    .body-part-grid {
        grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
        gap: var(--space-3);
    }
}

/* ============================================
   検索 & ステータスバー
   ============================================ */
.search-box {
    position: relative;
    margin-bottom: var(--space-4);
}

#search-input {
    width: 100%;
    padding: var(--space-2) var(--space-3);
    padding-left: 2.75rem;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    transition: all var(--transition-base);
    background: var(--color-surface);
    font-family: var(--font-base);
}

#search-input:focus {
    outline: none;
    border-color: var(--color-text-primary);
    box-shadow: 0 0 0 3px rgba(26, 26, 26, 0.05);
}

#search-input::placeholder {
    color: var(--color-text-tertiary);
}

.search-icon {
    position: absolute;
    left: var(--space-2);
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.125rem;
    color: var(--color-text-tertiary);
    pointer-events: none;
}

.status-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-2) 0;
    margin-bottom: var(--space-3);
    color: var(--color-text-secondary);
    font-size: 0.875rem;
}

.btn-refresh {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: var(--space-1) var(--space-2);
    cursor: pointer;
    transition: all var(--transition-fast);
    color: var(--color-text-secondary);
}

.btn-refresh:hover {
    background: var(--color-hover);
    border-color: var(--color-text-primary);
    color: var(--color-text-primary);
}

.btn-refresh:active {
    transform: scale(0.95);
}

.refresh-icon {
    font-size: 1.125rem;
    display: inline-block;
}

/* ============================================
   動画一覧 - カードデザインの品質向上
   ============================================ */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--space-4);
}

.video-card {
    border: 1px solid var(--color-border-subtle);
    border-radius: var(--radius-lg);
    overflow: hidden;
    background: var(--color-surface);
    cursor: pointer;
    transition: all var(--transition-base);
}

.video-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
    border-color: var(--color-border);
}

.video-card:active {
    transform: translateY(-2px);
}

.video-thumbnail {
    width: 100%;
    aspect-ratio: 16/9;
    object-fit: cover;
    background: linear-gradient(135deg, var(--color-hover) 0%, var(--color-border-subtle) 100%);
    display: block;
}

.video-card-body {
    padding: var(--space-3);
}

.video-card-title {
    font-size: 0.9375rem;
    font-weight: 500;
    margin-bottom: var(--space-2);
    line-height: 1.5;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    color: var(--color-text-primary);
    letter-spacing: -0.01em;
}

.video-card-meta {
    display: flex;
    gap: var(--space-1);
    flex-wrap: wrap;
    align-items: center;
}

.badge {
    display: inline-block;
    padding: 0.25rem 0.625rem;
    border-radius: var(--radius-xs);
    font-size: 0.75rem;
    font-weight: 500;
    background: var(--color-hover);
    color: var(--color-text-secondary);
    letter-spacing: 0;
}

.badge.palpation {
    background: var(--color-palpation-light);
    color: var(--color-palpation);
}

.badge.ortho {
    background: var(--color-ortho-light);
    color: var(--color-ortho);
}

.video-duration {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
    font-weight: 400;
}

@media (min-width: 640px) {
    .video-grid {
        grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    }
}

@media (min-width: 1024px) {
    .video-grid {
        grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    }
}

/* 空状態 */
.empty-state {
    text-align: center;
    padding: var(--space-8) var(--space-4);
    color: var(--color-text-tertiary);
    font-size: 0.9375rem;
}

/* 再生リストカード（API未使用時） */
.playlist-card {
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    background: var(--color-surface);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: var(--space-3);
    max-width: 500px;
    margin: 0 auto;
}

.playlist-card-icon {
    font-size: 3rem;
    opacity: 0.6;
}

.playlist-card-body {
    flex: 1;
}

.playlist-card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--space-2);
    letter-spacing: -0.02em;
}

.playlist-card-desc {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-3);
    font-size: 0.9375rem;
}

.playlist-card-meta {
    margin-bottom: var(--space-2);
}

.playlist-card .btn-youtube {
    width: 100%;
    max-width: 300px;
}

/* ============================================
   動画詳細 - プロフェッショナルなビュー
   ============================================ */
.video-detail {
    max-width: 900px;
    margin: 0 auto;
}

.video-player-wrapper {
    margin-bottom: var(--space-5);
    border-radius: var(--radius-lg);
    overflow: hidden;
    background: #000;
    box-shadow: var(--shadow-lg);
}

.video-player {
    position: relative;
    width: 100%;
    padding-top: 56.25%; /* 16:9 */
    background: linear-gradient(135deg, #1a1a1a 0%, #2a2a2a 100%);
}

.video-player iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.video-info {
    margin-bottom: var(--space-5);
}

.video-title {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--space-3);
    line-height: 1.4;
    letter-spacing: -0.02em;
    color: var(--color-text-primary);
}

.video-meta {
    display: flex;
    gap: var(--space-2);
    flex-wrap: wrap;
    margin-bottom: var(--space-3);
    align-items: center;
}

.video-duration {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.video-description {
    color: var(--color-text-secondary);
    line-height: 1.7;
    font-size: 0.9375rem;
}

.video-actions {
    display: flex;
    gap: var(--space-2);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    font-weight: 500;
    text-align: center;
    text-decoration: none;
    cursor: pointer;
    transition: all var(--transition-base);
    border: none;
    font-family: var(--font-base);
}

.btn-youtube {
    background: #ff0000;
    color: white;
    box-shadow: 0 2px 8px rgba(255, 0, 0, 0.2);
}

.btn-youtube:hover {
    background: #cc0000;
    box-shadow: 0 4px 16px rgba(255, 0, 0, 0.3);
    transform: translateY(-1px);
}

.btn-youtube:active {
    transform: translateY(0);
}

/* ============================================
   オフライン通知
   ============================================ */
.offline-notice {
    position: fixed;
    bottom: var(--space-4);
    left: var(--space-3);
    right: var(--space-3);
    background: #fffbf0;
    border: 1px solid #ffc107;
    border-radius: var(--radius-md);
    padding: var(--space-3);
    text-align: center;
    font-size: 0.875rem;
    box-shadow: var(--shadow-lg);
    z-index: 200;
    animation: slideUp 0.4s var(--transition-base);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================================
   フッター
   ============================================ */
.app-footer {
    text-align: center;
    padding: var(--space-5) var(--space-3);
    border-top: 1px solid var(--color-border-subtle);
    color: var(--color-text-tertiary);
    font-size: 0.8125rem;
    background: var(--color-bg);
}

.app-footer p {
    margin-bottom: var(--space-1);
}

.last-sync {
    margin-top: var(--space-1);
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
}

/* ============================================
   レスポンシブ（タブレット以上）
   ============================================ */
@media (min-width: 768px) {
    .screen-title {
        font-size: 2rem;
    }
}

/* ============================================
   ユーティリティ
   ============================================ */
.hidden {
    display: none !important;
}

/* フォーカス可視性 */
*:focus-visible {
    outline: 2px solid var(--color-text-primary);
    outline-offset: 2px;
}

button:focus-visible,
a:focus-visible {
    outline-offset: 3px;
}

/* スムーズスクロール */
html {
    scroll-behavior: smooth;
}

/* 選択テキストの色 */
::selection {
    background: var(--color-text-primary);
    color: white;
}