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

        :root {
            --primary: #1a1a1a;
            --primary-light: #2e2e2e;
            --primary-dark: #000000;
            --secondary: #1a1a1a;
            --success: #2f5132;
            --error: #7a2e2e;
            --warning: #6b5226;
            --gray-50: #faf7f2;
            --gray-100: #f3eee5;
            --gray-200: #e7e0d4;
            --gray-300: #d8cfc0;
            --gray-600: #6b6660;
            --gray-800: #2b2823;
            --gray-900: #181613;
            --border-radius: 6px;
            --transition: all 0.2s ease;
        }

        body {
            font-family: 'Times New Roman', Times, serif;
            background: #f5f0e6;
            color: var(--gray-900);
            min-height: 100vh;
            padding: 20px;
        }

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

        header {
            background: #ffffff;
            padding: 20px 24px;
            border-radius: var(--border-radius);
            border: 1px solid var(--gray-200);
            box-shadow: none;
            margin-bottom: 20px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 20px;
        }

        h1 {
            color: var(--gray-900);
            font-size: 26px;
            font-weight: 400;
            letter-spacing: 0.5px;
        }

        .header-stats {
            display: flex;
            gap: 30px;
            align-items: center;
        }

        .stat {
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        .stat-label {
            color: var(--gray-600);
            font-size: 12px;
            text-transform: uppercase;
            margin-bottom: 4px;
        }

        .stat-value {
            color: var(--gray-900);
            font-size: 20px;
            font-weight: 600;
        }

        .setup-screen {
            background: #ffffff;
            padding: 30px;
            border-radius: var(--border-radius);
            border: 1px solid var(--gray-200);
            box-shadow: none;
        }

        .setup-section {
            margin-bottom: 30px;
        }

        .setup-section h2 {
            color: var(--gray-900);
            margin-bottom: 15px;
            font-size: 18px;
        }

        .file-input-group {
            display: flex;
            gap: 10px;
            margin-bottom: 15px;
            flex-wrap: wrap;
        }

        input[type="file"] {
            padding: 10px;
            border: 1px solid var(--gray-300);
            border-radius: var(--border-radius);
            flex: 1;
            min-width: 200px;
            font-family: 'Times New Roman', Times, serif;
            background: #ffffff;
            color: var(--gray-900);
        }

        button {
            padding: 10px 22px;
            border: 1px solid var(--gray-900);
            border-radius: var(--border-radius);
            cursor: pointer;
            font-size: 14px;
            font-weight: 400;
            font-family: 'Times New Roman', Times, serif;
            background: transparent;
            color: var(--gray-900);
            transition: var(--transition);
        }

        .btn-primary {
            background: #ffffff;
            color: var(--gray-900);
            border: 2px solid var(--gray-900);
            font-weight: 700;
        }

        .btn-primary:hover {
            background: var(--gray-50);
        }

        .btn-secondary {
            background: transparent;
            color: var(--gray-900);
            border: 1px solid var(--gray-300);
        }

        .btn-secondary:hover {
            border-color: var(--gray-900);
            background: var(--gray-50);
        }

        .btn-success {
            background: #ffffff;
            color: var(--gray-900);
            border: 2px solid var(--gray-900);
            font-weight: 700;
        }

        .btn-success:hover {
            background: var(--gray-50);
        }

        .btn-disabled {
            background: var(--gray-100);
            color: var(--gray-600);
            border: 1px solid var(--gray-200);
            cursor: not-allowed;
        }

        .status-message {
            padding: 12px;
            border-radius: var(--border-radius);
            margin-bottom: 15px;
        }

        .status-success {
            background: var(--gray-50);
            color: var(--gray-900);
            border: 1px solid var(--success);
        }

        .status-error {
            background: var(--gray-50);
            color: var(--gray-900);
            border: 1px solid var(--error);
        }

        .status-info {
            background: var(--gray-50);
            color: var(--gray-900);
            border: 1px solid var(--gray-300);
        }

        .game-selection {
            background: #ffffff;
            padding: 30px;
            border-radius: var(--border-radius);
            border: 1px solid var(--gray-200);
            box-shadow: none;
            margin-bottom: 20px;
        }

        .game-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 20px;
            margin-top: 20px;
        }

        .game-card {
            background: var(--gray-50);
            padding: 20px;
            border-radius: var(--border-radius);
            cursor: pointer;
            border: 1px solid var(--gray-200);
            transition: var(--transition);
            text-align: center;
        }

        .game-card:hover {
            border-color: var(--gray-900);
            transform: none;
            box-shadow: none;
        }

        .game-card h3 {
            color: var(--gray-900);
            margin-bottom: 10px;
        }

        .game-card p {
            color: var(--gray-600);
            font-size: 14px;
            margin-bottom: 15px;
        }

        .game-screen {
            display: none;
            background: #ffffff;
            padding: 30px;
            border-radius: var(--border-radius);
            border: 1px solid var(--gray-200);
            box-shadow: none;
        }

        .game-screen.active {
            display: block;
        }

        .game-config {
            background: var(--gray-50);
            padding: 20px;
            border-radius: var(--border-radius);
            margin-bottom: 30px;
        }

        .config-row {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 20px;
            margin-bottom: 20px;
        }

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

        .config-group label {
            color: var(--gray-900);
            font-weight: 600;
            margin-bottom: 8px;
            font-size: 14px;
        }

        select, input[type="checkbox"] {
            padding: 10px;
            border: 1px solid var(--gray-300);
            border-radius: var(--border-radius);
            font-size: 14px;
            font-family: 'Times New Roman', Times, serif;
            background: #ffffff;
            color: var(--gray-900);
        }

        .checkbox-group {
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .quiz-row {
            display: flex;
            gap: 30px;
            margin-bottom: 30px;
            align-items: stretch;
        }

        .character-display {
            background: var(--gray-50);
            padding: 30px 20px;
            border-radius: var(--border-radius);
            text-align: center;
            min-height: 200px;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            flex: 0 1 420px;
            min-width: 280px;
            overflow: hidden;
        }

        .chinese-character {
            color: var(--primary);
            font-weight: 300;
            margin-bottom: 20px;
            font-family: 'Noto Sans SC', 'Microsoft YaHei', sans-serif;
            white-space: nowrap;
            line-height: 1.1;
        }

        .character-pinyin {
            font-size: 24px;
            color: var(--gray-800);
            font-weight: 500;
            margin-bottom: 20px;
            font-family: 'Monaco', 'Courier New', monospace;
        }

        .options-container {
            display: grid;
            gap: 12px;
            flex: 1 1 auto;
            align-content: center;
        }


        .option-button {
            padding: 15px;
            background: var(--gray-50);
            border: 1px solid var(--gray-300);
            border-radius: var(--border-radius);
            cursor: pointer;
            transition: var(--transition);
            text-align: left;
            font-size: 14px;
            font-family: 'Times New Roman', Times, serif;
            color: var(--gray-900);
        }

        .option-button:hover {
            border-color: var(--gray-900);
            background: var(--gray-100);
        }

        .option-button.correct {
            background: var(--gray-100);
            border-color: var(--success);
            color: var(--gray-900);
            cursor: not-allowed;
        }

        .option-button.incorrect {
            background: var(--gray-100);
            border-color: var(--error);
            color: var(--gray-900);
            cursor: not-allowed;
        }

        .option-button.disabled {
            cursor: not-allowed;
        }

        .character-details {
            background: var(--gray-50);
            padding: 25px;
            border-radius: var(--border-radius);
            margin-bottom: 30px;
            display: none;
        }

        .character-details.show {
            display: block;
        }

        .details-columns {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 0 40px;
        }

        .details-column:last-child .detail-section:last-child {
            margin-bottom: 0;
        }

        .detail-section {
            margin-bottom: 20px;
        }

        .detail-section:last-child {
            margin-bottom: 0;
        }

        .detail-title {
            color: var(--gray-900);
            font-weight: 600;
            margin-bottom: 8px;
            font-size: 13px;
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        .detail-content {
            color: var(--gray-800);
            line-height: 1.6;
        }

        .transcription {
            background: var(--gray-50);
            padding: 10px;
            border-radius: 4px;
            margin-bottom: 8px;
            font-family: 'Monaco', 'Courier New', monospace;
            font-size: 13px;
        }

        .transcription-label {
            color: var(--gray-600);
            font-weight: 600;
            font-size: 12px;
            display: block;
            margin-bottom: 4px;
        }

        .transcriptions-hover {
            position: relative;
            display: inline-block;
            cursor: help;
        }

        .transcriptions-hover .hover-label {
            color: var(--gray-900);
            font-weight: 600;
            padding: 4px 8px;
            border-radius: 4px;
            background: var(--gray-100);
            text-decoration: underline;
            text-decoration-style: dotted;
        }

        .transcriptions-hover .hover-content {
            position: absolute;
            bottom: 100%;
            left: 50%;
            transform: translateX(-50%);
            background: var(--gray-900);
            color: var(--gray-50);
            padding: 15px;
            border-radius: var(--border-radius);
            z-index: 1000;
            margin-bottom: 10px;
            font-family: 'Monaco', 'Courier New', monospace;
            font-size: 12px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.2);
            display: none;
            min-width: 250px;
        }

        .transcriptions-hover:hover .hover-content {
            display: block;
        }

        .transcriptions-hover .hover-content::after {
            content: '';
            position: absolute;
            top: 100%;
            left: 50%;
            transform: translateX(-50%);
            border: 6px solid transparent;
            border-top-color: var(--gray-900);
        }

        .form-group-label {
            color: var(--gray-600);
            font-size: 12px;
            text-transform: uppercase;
            letter-spacing: 0.5px;
            margin: 10px 0 6px;
        }

        .form-group-label:first-child {
            margin-top: 0;
        }

        .cjk-hover {
            position: relative;
            display: inline-block;
            cursor: help;
        }

        .cjk-hover-trigger {
            color: var(--gray-900);
            font-weight: 600;
            text-decoration: underline;
            text-decoration-style: dotted;
            text-decoration-color: var(--gray-600);
        }

        .cjk-hover-content {
            position: absolute;
            bottom: 100%;
            left: 50%;
            transform: translateX(-50%);
            background: var(--gray-900);
            color: var(--gray-50);
            padding: 12px;
            border-radius: var(--border-radius);
            z-index: 1000;
            margin-bottom: 10px;
            font-size: 12px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.2);
            display: none;
            min-width: 220px;
            max-width: 320px;
            text-align: left;
            white-space: normal;
        }

        .cjk-hover:hover .cjk-hover-content {
            display: block;
        }

        .cjk-hover-content::after {
            content: '';
            position: absolute;
            top: 100%;
            left: 50%;
            transform: translateX(-50%);
            border: 6px solid transparent;
            border-top-color: var(--gray-900);
        }

        .cjk-hover-entry {
            padding: 6px 0;
            border-top: 1px solid rgba(255,255,255,0.15);
        }

        .cjk-hover-entry:first-child {
            padding-top: 0;
            border-top: none;
        }

        .cjk-hover-word {
            font-family: 'Noto Sans SC', 'Microsoft YaHei', sans-serif;
            font-size: 16px;
            font-weight: 600;
            margin-bottom: 4px;
        }

        .cjk-hover-pinyin {
            font-family: 'Monaco', 'Courier New', monospace;
            font-size: 11px;
            font-weight: 400;
            color: var(--gray-300);
        }

        .cjk-hover-meaning {
            line-height: 1.4;
        }

        .cjk-hover-noinfo {
            color: var(--gray-300);
            font-style: italic;
        }

        .transcription-item {
            margin-bottom: 8px;
            line-height: 1.4;
        }

        .transcription-item:last-child {
            margin-bottom: 0;
        }

        .transcription-item-label {
            font-weight: 600;
            color: var(--gray-50);
            display: inline;
            margin-right: 6px;
        }

        .meanings-list {
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
        }

        .meaning-tag {
            background: var(--gray-50);
            padding: 6px 12px;
            border-radius: 20px;
            font-size: 13px;
            border: 1px solid var(--gray-300);
        }

        .pos-tag {
            background: var(--gray-900);
            color: #ffffff;
            padding: 4px 8px;
            border-radius: 4px;
            font-size: 12px;
            margin-right: 4px;
        }

        .controls {
            display: flex;
            gap: 10px;
            justify-content: center;
            margin-bottom: 20px;
            flex-wrap: wrap;
        }

        .progress-bar {
            width: 100%;
            height: 8px;
            background: var(--gray-200);
            border-radius: 4px;
            overflow: hidden;
            margin-bottom: 20px;
        }

        .progress-fill {
            height: 100%;
            background: var(--gray-900);
            transition: width 0.3s ease;
        }

        .session-stats {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 15px;
            background: var(--gray-50);
            padding: 20px;
            border-radius: var(--border-radius);
            margin-bottom: 30px;
        }

        .vocab-grid {
            display: grid;
            grid-template-columns: repeat(10, 1fr);
            gap: 10px;
            margin-bottom: 30px;
        }

        .vocab-box {
            background: var(--gray-50);
            border: 1px solid var(--gray-300);
            border-radius: var(--border-radius);
            padding: 12px 6px;
            text-align: center;
            cursor: pointer;
            transition: var(--transition);
        }

        .vocab-box:hover {
            border-color: var(--gray-900);
            background: var(--gray-100);
        }

        .vocab-box.selected {
            border-color: var(--gray-900);
            border-width: 2px;
            background: var(--gray-100);
        }

        .vocab-box-word {
            font-family: 'Noto Sans SC', 'Microsoft YaHei', sans-serif;
            font-size: 26px;
            color: var(--gray-900);
            line-height: 1.2;
            white-space: nowrap;
        }

        .vocab-box-pinyin {
            font-family: 'Monaco', 'Courier New', monospace;
            font-size: 11px;
            color: var(--gray-600);
            margin-top: 4px;
        }

        .vocab-detail-row {
            grid-column: 1 / -1;
            background: var(--gray-50);
            border: 1px solid var(--gray-300);
            border-radius: var(--border-radius);
            padding: 20px;
            margin: 0;
        }

        .session-stat {
            text-align: center;
        }

        .session-stat-label {
            color: var(--gray-600);
            font-size: 12px;
            margin-bottom: 8px;
        }

        .session-stat-value {
            color: var(--gray-900);
            font-size: 28px;
            font-weight: 700;
        }

        .hidden {
            display: none;
        }

        @media (max-width: 768px) {
            header {
                flex-direction: column;
                align-items: flex-start;
            }

            .header-stats {
                width: 100%;
                justify-content: flex-start;
            }

            .config-row {
                grid-template-columns: 1fr;
            }

            .game-grid {
                grid-template-columns: 1fr;
            }

            .quiz-row {
                flex-direction: column;
            }

            .character-display {
                flex: 1 1 auto;
            }

            .details-columns {
                grid-template-columns: 1fr;
                gap: 0;
            }

            .vocab-grid {
                grid-template-columns: repeat(4, 1fr);
            }
        }

        @media (max-width: 1100px) and (min-width: 769px) {
            .vocab-grid {
                grid-template-columns: repeat(6, 1fr);
            }
        }

        @media (max-width: 420px) {
            .vocab-grid {
                grid-template-columns: repeat(3, 1fr);
            }

            .vocab-box-word {
                font-size: 22px;
            }
        }
        /* ===== Audio button ===== */
        .audio-btn {
            background: none;
            border: 1px solid var(--gray-300);
            border-radius: 4px;
            cursor: pointer;
            font-size: 14px;
            padding: 2px 6px;
            line-height: 1;
            color: var(--gray-600);
            transition: var(--transition);
            display: inline-block;
        }
        .audio-btn:hover {
            background: var(--gray-100);
            border-color: var(--gray-600);
        }

        /* ===== Sentence examples in character details ===== */
        .sentence-example {
            margin-bottom: 10px;
            padding: 8px 10px;
            background: var(--gray-50);
            border-radius: var(--border-radius);
            border-left: 3px solid var(--gray-300);
        }
        .sentence-mandarin {
            font-size: 17px;
            color: var(--gray-900);
        }
        .sentence-meaning {
            font-size: 13px;
            color: var(--gray-600);
            margin-top: 4px;
            font-style: italic;
        }

        /* ===== Login screen ===== */
        #login-screen input[type="text"],
        #login-screen input[type="password"] {
            outline: none;
        }
        #login-screen input:focus {
            border-color: var(--gray-800) !important;
        }

        /* ===== Strength import panel ===== */
        #strength-upload-panel {
            background: var(--gray-50);
            border: 1px solid var(--gray-200);
            border-radius: var(--border-radius);
        }