:root {
    --primary-color: #6C5CE7;
    --primary-hover: #5A4BCE;
    --bg-color: #F8F9FA;
    --card-bg: #FFFFFF;
    --text-main: #2D3436;
    --text-muted: #636E72;
    --correct-color: #81ECEC;
    --incorrect-color: #FF7675;
    --sidebar-bg: #2D3436;
    --sidebar-text: #DFE6E9;
    --border-color: #E0E0E0;
    --font-scale: 1;
}

/* ダークモード用の変数上書き */
body.dark-mode {
    --bg-color: #121212;
    --card-bg: #1E1E1E;
    --text-main: #E0E0E0;
    --text-muted: #A0A0A0;
    --sidebar-bg: #1A1A1A;
    --border-color: #333333;
    --primary-color: #8C7DFF;
    --primary-hover: #7564E6;
}

* { 
    box-sizing: border-box; 
    margin: 0; 
    padding: 0; 
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; 
    -webkit-tap-highlight-color: transparent; /* スマホタップ時の青枠を消去 */
}

body { 
    background-color: var(--bg-color); 
    color: var(--text-main); 
    display: flex; 
    height: 100vh; 
    height: 100dvh; /* モバイルブラウザのツールバー対策 */
    overflow: hidden; 
    transition: background-color 0.3s, color 0.3s; 
}

.app-container { display: flex; width: 100%; height: 100%; position: relative; }

/* --- サイドバー --- */
.sidebar { width: 280px; background-color: var(--sidebar-bg); color: var(--sidebar-text); display: flex; flex-direction: column; z-index: 20; transition: 0.3s ease; }
.sidebar-header { display: flex; flex-direction: column; gap: 10px; padding: 20px; background-color: rgba(0,0,0,0.2); }
.category-nav { flex-grow: 1; overflow-y: auto; padding: 10px 0; }
.action-btn { padding: 8px 12px; border: none; border-radius: 6px; cursor: pointer; font-size: 0.9rem; font-weight: bold; transition: 0.2s; }
.add-btn { background-color: var(--primary-color); color: white; width: 100%; }
.folder-header { display: flex; justify-content: space-between; align-items: center; padding: 10px 15px; background-color: rgba(255,255,255,0.05); margin-top: 5px; cursor: pointer; user-select: none; transition: background-color 0.2s; }
.folder-title { font-weight: bold; font-size: 0.9rem; color: #B2BEC3; }
.folder-toggle-icon { display: inline-block; width: 18px; font-size: 0.8rem; transition: transform 0.2s ease; }
.folder.open .folder-toggle-icon { transform: rotate(90deg); }
.icon-btn { background: transparent; border: 1px solid rgba(255,255,255,0.2); color: #FFF; border-radius: 4px; padding: 4px 8px; cursor: pointer; font-size: 0.8rem; margin-left: 2px; }
.set-wrapper { display: flex; justify-content: space-between; align-items: center; padding: 5px 15px 5px 25px; transition: 0.2s; }
.set-btn { flex-grow: 1; text-align: left; background: none; border: none; color: var(--sidebar-text); cursor: pointer; padding: 8px 0; font-size: 0.95rem; }
.set-btn-group { display: flex; gap: 4px; }

/* サイドバー・フッター */
.sidebar-footer { padding: 15px; background-color: rgba(0,0,0,0.3); display: flex; flex-direction: column; gap: 10px; }
.toggle-label { display: flex; align-items: center; gap: 8px; font-size: 0.9rem; cursor: pointer; color: #DFE6E9; }
.sidebar-btn { width: 100%; text-align: center; }
.sync-status { font-size: 0.75rem; color: #A0A0A0; text-align: center; margin-top: -5px; }
.sync-status.active { color: #00B894; }
.sidebar .outline-btn { color: #DFE6E9 !important; border-color: rgba(255, 255, 255, 0.3) !important; }

/* サイドバー開閉トグル */
.sidebar { transition: width 0.3s ease, padding 0.3s ease; }
.sidebar.collapsed { width: 0; padding: 0; overflow: hidden; }
.sidebar-toggle-btn { position: absolute; top: 50%; left: 280px; transform: translateY(-50%); background-color: var(--primary-color); color: white; border: none; width: 24px; height: 60px; border-radius: 0 8px 8px 0; cursor: pointer; z-index: 50; transition: left 0.3s ease; display: flex; align-items: center; justify-content: center; font-size: 0.8rem; box-shadow: 3px 0 6px rgba(0,0,0,0.15); }
.sidebar.collapsed ~ .sidebar-toggle-btn { left: 0; }

/* --- メインコンテンツ --- */
.main-content { flex-grow: 1; padding: 20px 40px; overflow-y: auto; position: relative; }
.mobile-menu-btn { display: none; }
.screen { display: none; animation: fadeIn 0.3s ease; max-width: 800px; margin: 0 auto; }
.screen.active { display: block; }
#question-text, #explanation-text { white-space: pre-wrap; }

/* --- クイズ画面 --- */
.quiz-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; padding-bottom: 15px; border-bottom: 2px solid var(--border-color); }
.progress-indicator { color: var(--text-muted); font-weight: bold; }
.question-card { background: var(--card-bg); padding: 30px; border-radius: 12px; box-shadow: 0 4px 15px rgba(0,0,0,0.05); font-size: calc(1.1rem * var(--font-scale)); line-height: 1.6; margin-bottom: 25px; }
.choices-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 15px; margin-bottom: 30px; }
.choice-btn { background: var(--card-bg); border: 2px solid var(--border-color); padding: 15px; border-radius: 8px; font-size: calc(1rem * var(--font-scale)); color: var(--text-main); cursor: pointer; text-align: left; transition: 0.15s ease; white-space: pre-wrap; }
.choice-btn.selected { border-color: var(--primary-color); background-color: rgba(108, 92, 231, 0.1); box-shadow: 0 4px 10px rgba(108, 92, 231, 0.15); }
.choice-btn.correct { background-color: rgba(0, 184, 148, 0.1); border-color: #00B894; color: #00B894; font-weight: bold; }
.choice-btn.incorrect { background-color: rgba(214, 48, 49, 0.1); border-color: #D63031; color: #D63031; }
.choice-btn.eliminated { text-decoration: line-through; opacity: 0.4; background-color: transparent !important; border-style: dashed; border-color: var(--text-muted); }

.feedback-area { background: var(--card-bg); padding: 25px; border-radius: 12px; box-shadow: 0 4px 15px rgba(0,0,0,0.05); border-left: 6px solid var(--primary-color); }
.feedback-area.hidden { display: none; }
.badge { display: inline-block; padding: 6px 12px; border-radius: 20px; color: white; font-weight: bold; margin-bottom: 15px; }
.badge.correct { background-color: #00B894; }
.badge.incorrect { background-color: #D63031; }

/* --- 結果・振り返り画面 --- */
.result-box { background: var(--card-bg); padding: 40px; border-radius: 12px; box-shadow: 0 4px 20px rgba(0,0,0,0.08); border: 1px solid var(--border-color); }
.result-header { display: flex; align-items: center; gap: 15px; margin-bottom: 10px; flex-wrap: wrap; }
.attempt-badge { background: rgba(108, 92, 231, 0.1); color: var(--primary-color); padding: 4px 12px; border-radius: 6px; font-size: 0.85rem; font-weight: bold; }
.result-meta { color: var(--text-muted); font-size: 0.95rem; margin-bottom: 30px; display: flex; gap: 20px; }
.result-stats-container { display: flex; align-items: center; gap: 50px; margin-bottom: 40px; flex-wrap: wrap; }
.chart-circle { width: 180px; height: 180px; border-radius: 50%; display: flex; align-items: center; justify-content: center; background: conic-gradient(#55EFC4 var(--p), #FF7675 0); }
.chart-inner { width: 130px; height: 130px; background: var(--card-bg); border-radius: 50%; }
.score-percentage { font-size: 4rem; font-weight: 300; line-height: 1; }
.percent-symbol { font-size: 2rem; margin-left: 5px; }
.score-fraction { font-size: 1.1rem; color: var(--text-muted); margin-left: 15px; }
.result-actions { display: flex; gap: 15px; flex-wrap: wrap; }
.review-filters { display: flex; gap: 10px; }
.filter-btn { padding: 6px 12px; border: 1px solid var(--border-color); background: var(--card-bg); color: var(--text-main); border-radius: 20px; cursor: pointer; }
.filter-btn.active { background: var(--primary-color); color: white; border-color: var(--primary-color); }
.review-list { display: flex; flex-direction: column; gap: 20px; margin-bottom: 30px; }
.review-item { background: var(--card-bg); padding: 20px; border-radius: 10px; border-left: 5px solid var(--border-color); box-shadow: 0 2px 10px rgba(0,0,0,0.05); }
.review-item.correct { border-left-color: #00B894; }
.review-item.incorrect { border-left-color: #D63031; }
.review-q, .review-exp { font-size: calc(1rem * var(--font-scale)); white-space: pre-wrap; }
.review-q { font-weight: bold; margin-bottom: 15px; }
.review-exp { margin-top: 10px; padding-top: 10px; border-top: 1px dashed var(--border-color); color: var(--text-muted); }

/* --- 共通ボタン --- */
.btn { padding: 12px 24px; border: none; border-radius: 6px; font-size: 1rem; cursor: pointer; transition: 0.2s; font-weight: bold; }
.primary-btn { background-color: var(--primary-color); color: white; }
.secondary-btn { background-color: #DFE6E9; color: #2D3436; }
.outline-btn { background-color: transparent; border: 1px solid var(--text-muted); color: var(--text-main); }
body.dark-mode .secondary-btn { background-color: #444; color: #FFF; }

/* --- モーダル設定 --- */
.modal-overlay { 
    position: fixed; 
    top: 0; 
    left: 0; 
    width: 100%; 
    height: 100%; 
    background: rgba(0, 0, 0, 0.5); /* 共通：半透明背景 */
    display: flex; 
    justify-content: center; 
    align-items: center; 
    z-index: 100; 
    backdrop-filter: blur(2px); /* 背景ぼかし効果 */
}

/* ログインモーダルのみ単色背景（テーマ色に連動） */
#login-modal.modal-overlay {
    background: var(--bg-color);
    backdrop-filter: none;
}

.modal-overlay.hidden { display: none; }
.modal-content { background: var(--card-bg); padding: 30px; border-radius: 12px; width: 400px; text-align: center; box-shadow: 0 10px 25px rgba(0,0,0,0.15); }
.modal-content h3 { margin-bottom: 10px; }
.modal-content p { color: var(--text-muted); margin-bottom: 25px; }
.modal-actions { display: flex; flex-direction: column; gap: 10px; }

/* --- 学習ヒートマップ --- */
.heatmap-section { background: var(--card-bg); padding: 25px; border-radius: 12px; box-shadow: 0 4px 15px rgba(0,0,0,0.05); margin-top: 20px; }
.heatmap-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 15px; }
.heatmap-header h2 { font-size: 1.2rem; }
.heatmap-select { padding: 6px 10px; border-radius: 6px; border: 1px solid var(--border-color); background: var(--bg-color); color: var(--text-main); font-size: 0.9rem; }
.heatmap-scroll { overflow-x: auto; padding-bottom: 10px; }
.heatmap-container { display: flex; gap: 8px; padding-top: 5px; }
.heatmap-y-axis { display: grid; grid-template-rows: repeat(7, 10px); gap: 3px; font-size: 0.65rem; color: var(--text-muted); text-align: right; margin-top: 20px; }
.heatmap-main { display: flex; flex-direction: column; position: relative; }
.heatmap-x-axis { display: flex; font-size: 0.75rem; color: var(--text-muted); height: 16px; position: relative; margin-bottom: 4px; }
.heatmap-grid { display: grid; grid-template-rows: repeat(7, 10px); grid-auto-flow: column; gap: 3px; width: max-content; }
.day-square { width: 10px; height: 10px; border-radius: 2px; background-color: var(--border-color); position: relative; cursor: pointer; }
.heatmap-legend { display: flex; align-items: center; justify-content: flex-end; gap: 5px; font-size: 0.8rem; color: var(--text-muted); margin-top: 10px; }
.legend-box { width: 10px; height: 10px; border-radius: 2px; }

.level-0 { background-color: var(--border-color); }
.level-1 { background-color: #9BE9A8; }
.level-2 { background-color: #40C463; }
.level-3 { background-color: #30A14E; }
.level-4 { background-color: #216E39; }

body.dark-mode .level-0 { background-color: #2D333B; }
body.dark-mode .level-1 { background-color: #0E4429; }
body.dark-mode .level-2 { background-color: #006D32; }
body.dark-mode .level-3 { background-color: #26A641; }
body.dark-mode .level-4 { background-color: #39D353; }

#welcome-screen { max-width: 1000px; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
@keyframes shake { 0%, 100% { transform: translateX(0); } 25% { transform: translateX(-5px); } 75% { transform: translateX(5px); } }
.shake { animation: shake 0.3s; }

/* ==========================================
   PC向けHover設定（タッチ時のスタイルべたつき防止）
   ========================================== */
@media (hover: hover) {
    .choice-btn:hover:not(:disabled) {
        border-color: var(--primary-color);
        transform: translateY(-2px);
        box-shadow: 0 4px 10px rgba(108, 92, 231, 0.15);
    }
    .action-btn:hover { opacity: 0.9; }
    .add-btn:hover { background-color: var(--primary-hover); }
    .icon-btn:hover { background-color: rgba(255,255,255,0.2); }
    .folder-header:hover { background-color: rgba(255,255,255,0.1); }
    .primary-btn:hover { background-color: var(--primary-hover); }
    .secondary-btn:hover { background-color: #B2BEC3; }
    .sidebar-toggle-btn:hover { background-color: var(--primary-hover); }
}

/* ==========================================
   スマホ・タッチ操作向けUI徹底最適化
   ========================================== */

/* タップした瞬間（:active）の押し込みフィードバック */
.choice-btn:active:not(:disabled),
.btn:active,
.action-btn:active,
.filter-btn:active {
    transform: scale(0.97) !important;
    opacity: 0.85;
    transition: transform 0.05s ease, opacity 0.05s ease;
}

@media (max-width: 768px) {
    /* 1. 全体レイアウト & iPhoneのノッチ/ホームバー対応 */
    .main-content { 
        padding: 12px 12px calc(20px + env(safe-area-inset-bottom)) 12px; 
    }
    .sidebar-toggle-btn { display: none; }
    
    /* iPhoneでの入力時自動ズーム防止（16px維持） */
    input[type="text"], input[type="password"], select {
        font-size: 16px !important;
    }

    /* 2. スマホ用ヘッダーメニューボタン */
    .mobile-menu-btn {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 100%;
        min-height: 48px;
        margin-bottom: 12px;
        background: var(--card-bg);
        border: 1px solid var(--border-color);
        border-radius: 10px;
        font-size: 1rem;
        font-weight: bold;
        color: var(--text-main);
        box-shadow: 0 2px 8px rgba(0,0,0,0.04);
    }

    /* 3. サイドバーのスマホ表示 */
    .sidebar { position: fixed; left: -280px; height: 100%; shadow: 4px 0 15px rgba(0,0,0,0.3); }
    .sidebar.open { left: 0; }
    .mobile-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.5); z-index: 15; backdrop-filter: blur(2px); }
    .mobile-overlay.hidden { display: none; }

    /* 4. クイズ画面の押しやすさ向上 */
    .quiz-header { margin-bottom: 12px; padding-bottom: 10px; }
    .question-card { padding: 18px 15px; margin-bottom: 15px; border-radius: 10px; }
    
    /* 選択肢を1列にし、タップしやすい縦幅（52px以上）に統一 */
    .choices-grid { grid-template-columns: 1fr; gap: 10px; margin-bottom: 20px; }
    .choice-btn { 
        min-height: 52px; 
        padding: 14px 16px; 
        border-radius: 10px;
        display: flex;
        align-items: center;
    }

    /* 5. 解説画面：「次の問題へ」ボタンを画面下部に固定（親指ゾーン配置） */
    .feedback-area { 
        padding: 15px 15px 80px 15px; /* 下部ボタン用の余白確保 */
        border-radius: 10px; 
    }

    #next-btn {
        position: fixed;
        bottom: calc(12px + env(safe-area-inset-bottom));
        left: 12px;
        right: 12px;
        width: calc(100% - 24px);
        z-index: 90;
        box-shadow: 0 6px 20px rgba(108, 92, 231, 0.4);
        padding: 15px;
        font-size: 1.05rem;
        border-radius: 12px;
    }

    /* 6. モーダル画面のコンパクト化 */
    .modal-content { 
        width: 88%; 
        max-width: 330px; 
        padding: 22px 18px; 
        border-radius: 16px; 
    }
    .modal-content h3 { font-size: 1.15rem; }
    .modal-content p { font-size: 0.9rem; margin-bottom: 18px; }

    /* 7. 結果画面 & 振り返り画面の最適化 */
    .result-box { padding: 18px 15px; border-radius: 10px; }
    .result-meta { flex-direction: column; gap: 4px; margin-bottom: 20px; font-size: 0.85rem; }
    .result-stats-container { gap: 15px; flex-direction: column; justify-content: center; margin-bottom: 20px; }
    .chart-circle { width: 140px; height: 140px; }
    .chart-inner { width: 100px; height: 100px; }
    .score-percentage { font-size: 3rem; }
    .percent-symbol { font-size: 1.5rem; }
    .score-fraction { font-size: 0.95rem; margin-left: 0; display: block; margin-top: 4px; }
    
    .btn { padding: 12px 16px; font-size: 0.95rem; width: 100%; border-radius: 8px; }
    .result-actions, .review-filters { flex-direction: column; gap: 8px; }

    /* 8. ヒートマップのなめらかなタッチスクロール */
    .heatmap-section { padding: 15px; border-radius: 10px; }
    .heatmap-scroll { -webkit-overflow-scrolling: touch; padding-bottom: 10px; }
}

/* ==========================================
   追加機能：プログレスバー、ストリーク、消去法
   ========================================== */

/* プログレスバー */
.progress-bar-bg {
    width: 100%;
    height: 6px;
    background-color: var(--border-color);
    border-radius: 3px;
    margin-bottom: 20px;
    overflow: hidden;
}
.progress-bar-fill {
    height: 100%;
    background-color: var(--primary-color);
    width: 0%;
    transition: width 0.4s ease;
}

/* 連続学習ストリークバッジ */
.streak-badge {
    display: inline-block;
    background: linear-gradient(135deg, #ff9a9e 0%, #fecfef 99%, #fecfef 100%);
    color: #d63031;
    font-weight: bold;
    padding: 8px 16px;
    border-radius: 20px;
    margin: 10px 0 15px 0;
    font-size: 1.05rem;
    box-shadow: 0 4px 15px rgba(214, 48, 49, 0.2);
}
body.dark-mode .streak-badge {
    background: linear-gradient(135deg, #4a1c1c 0%, #2d1414 100%);
    color: #ff7675;
}

/* 苦手再テストボタン */
.weak-btn {
    border-color: #ff7675;
    color: #ff7675;
    margin-top: 10px;
}
body.dark-mode .weak-btn {
    border-color: #ff7675;
    color: #ff7675;
}

/* スマホ長押し時の文字選択・メニュー表示をブロック（超重要） */
.choice-btn {
    user-select: none;
    -webkit-user-select: none;
    -webkit-touch-callout: none;
}


/* 月のラベルテキスト */
.month-label {
    position: absolute;
    top: 0;
    white-space: nowrap;
    transform: translateX(0);
}