/* CSS 变量定义 (默认主题) */
:root {
    --primary-color: #667eea;
    --primary-color-dark: #764ba2;
    --primary-color-light: #e0e7fa;
    --secondary-color: #f093fb;
    --secondary-color-dark: #f5576c;

    --text-color: #2d3748;
    --text-color-secondary: #4a5568;
    --text-color-light: #a0aec0; /* 用于次要信息或提示 */

    --background-color: #f7fafc;
    --background-color-light: #ffffff;
    --background-color-dark: #edf2f7; /* 用于深色背景的渐变起始色 */

    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --hover-color: #f0f4f8; /* 通用悬停背景色 */

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);

    --word-display-bg: linear-gradient(135deg, var(--background-color-dark), var(--border-color));
    --word-display-text: var(--text-color);
    --word-display-outline-color: var(--border-color);

    --answer-display-bg: linear-gradient(135deg, #e3f2fd, #bbdefb);
    --answer-display-text: #1976d2;
    --answer-spoiler-bg: linear-gradient(135deg, #2d3748, #4a5568);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #fff3e0, #ffe0b2);
    --explanation-display-text: #e65100;
    --explanation-border: #ffb74d;
    --explanation-spoiler-bg: linear-gradient(135deg, #5d4037, #795548);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--primary-color), var(--primary-color-dark));
    --button-bg-feature: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-settings: linear-gradient(135deg, #4facfe, #00f2fe);
    --button-bg-deck: linear-gradient(135deg, #5ee7df, #b490ca);
    --button-bg-danger: linear-gradient(135deg, #e10a0a, #eb1a0f);
    --button-text-light: white;
    --button-text-dark: var(--text-color);
}

/* CSS 变量定义 (默认主题) */
:root {
    --primary-color: #667eea;
    --primary-color-dark: #764ba2;
    --primary-color-light: #e0e7fa;
    --secondary-color: #f093fb;
    --secondary-color-dark: #f5576c;

    --text-color: #2d3748;
    --text-color-secondary: #4a5568;
    --text-color-light: #a0aec0; /* 用于次要信息或提示 */

    --background-color: #f7fafc;
    --background-color-light: #ffffff;
    --background-color-dark: #edf2f7; /* 用于深色背景的渐变起始色 */

    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --hover-color: #f0f4f8; /* 通用悬停背景色 */

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);

    --word-display-bg: linear-gradient(135deg, var(--background-color-dark), var(--border-color));
    --word-display-text: var(--text-color);
    --word-display-outline-color: var(--border-color);

    --answer-display-bg: linear-gradient(135deg, #e3f2fd, #bbdefb);
    --answer-display-text: #1976d2;
    --answer-spoiler-bg: linear-gradient(135deg, #2d3748, #4a5568);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #fff3e0, #ffe0b2);
    --explanation-display-text: #e65100;
    --explanation-border: #ffb74d;
    --explanation-spoiler-bg: linear-gradient(135deg, #5d4037, #795548);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--primary-color), var(--primary-color-dark));
    --button-bg-feature: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-settings: linear-gradient(135deg, #4facfe, #00f2fe);
    --button-bg-deck: linear-gradient(135deg, #5ee7df, #b490ca);
    --button-bg-danger: linear-gradient(135deg, #e10a0a, #eb1a0f);
    --button-text-light: white;
    --button-text-dark: var(--text-color);
}

/* 基础样式 (保留基本结构) */
body {
    font-family: 'Noto Sans SC', 'Noto Sans Arabic', sans-serif;
    background-color: var(--background-color);
    margin: 0;
    padding: 0;
    line-height: 1.6;
    color: var(--text-color);
    text-align: center; /* 全局文本居中 */
}

.app-container {
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
    padding-bottom: 80px;
    min-height: 100vh;
    box-sizing: border-box;
    position: relative;
    display: flex; /* 应用flex布局 */
    flex-direction: column; /* 垂直方向排列 */
    /* justify-content: center; */ /* 如果需要整个应用内容垂直居中 */
    align-items: center; /* 水平居中 */
}

.page {
    display: none;
    position: relative;
    width: 100%;
}

.page.active {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: flex-start;
    flex-grow: 1;
    width: 100%;
    min-height: calc(100vh - 80px);
}

@media (prefers-reduced-motion: no-preference) {
    .page.active {
        animation: fadeIn 0.3s ease-in;
    }

    .import-message {
        animation: fadeInDown 0.5s;
    }

    #completion-screen {
        animation: bounceIn 0.5s ease-out;
    }

    .timer-progress {
        animation: countdown 5s linear forwards;
    }

    .skeleton-item {
        animation: pulse 1.5s infinite ease-in-out;
    }

    .nav-btn, .btn, .flashcard, .settings-section, .feature-section, #mode-selection-container label, .online-lexicon-item, .definition-toggle-btn, #import-modal .close-button, .slider {
        transition: all 0.3s ease;
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

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

.page-content {
    padding: 1.5rem;
}

.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: 600px;
    background: #ffffff;
    display: flex;
    justify-content: space-around;
    padding: 0.5rem 0;
    box-shadow: 0 -4px 12px rgba(0,0,0,0.1);
    z-index: 1000;
}

.nav-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    background: none;
    border: none;
    padding: 0.5rem;
    color: #666;
    font-size: 0.8rem;
    cursor: pointer;
    flex: 1;
}

.nav-btn.active {
    color: #667eea;
    position: relative;
}

.nav-btn.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 50%;
    transform: translateX(-50%);
    width: 4px;
    height: 4px;
    background-color: #667eea;
    border-radius: 50%;
}

@media (max-width: 380px) {
    .page-content {
        padding: 0.75rem;
    }

    .feature-section,
    .settings-section {
        padding: 1rem 0.75rem;
    }

    .nav-btn span {
        font-size: 0.65rem;
    }

    .nav-btn i {
        font-size: 1rem;
    }

    #card-container {
        padding: 1rem;
    }

    .btn {
        padding: 0.75rem 0.5rem;
        font-size: 0.9rem;
    }
}

.word-display, .answer-display {
    word-wrap: break-word;
    overflow-wrap: break-word;
    max-width: 100%;
}

[dir="rtl"] {
    text-align: right;
    font-family: 'Noto Sans Arabic', 'Traditional Arabic', Arial, sans-serif;
}

.btn:active {
    transform: scale(0.98);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

#forgot-btn:active { background-color: #d32f2f; }
#hard-btn:active { background-color: #ff9800; }
#easy-btn:active { background-color: #4caf50; }

#notification-container {
    position: fixed;
    top: 80px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2000;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
}

.import-message {
    padding: 1rem 1.5rem;
    border-radius: 8px;
    color: white;
    font-weight: bold;
    max-width: 90%;
    text-align: center;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.import-success {
    background: linear-gradient(135deg, #4caf50, #45a049);
}

.import-error {
    background: linear-gradient(135deg, #f44336, #d32f2f);
}

/* 基础按钮样式 */
.btn {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    margin: 0.3rem;
    background: var(--button-bg-primary);
    color: var(--button-text-light);
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    text-align: center;
    text-decoration: none;
    cursor: pointer;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
    font-family: 'Noto Sans SC', sans-serif;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
}

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

/* 功能按钮样式 */
.feature-btn {
    background: var(--button-bg-feature);
    width: 100%;
    margin: 0.5rem 0;
    padding: 1rem;
}

.feature-btn:hover {
    background: linear-gradient(135deg, #e668b4 0%, #e23366 100%); /* Keep original hover for now */
}

/* 设置按钮样式 */
.settings-btn {
    background: var(--button-bg-settings);
    width: 100%;
    margin: 0.3rem 0;
}

.settings-btn:hover {
    background: linear-gradient(135deg, #3a8fd4 0%, #00c8d4 100%); /* Keep original hover for now */
}

.settings-btn.danger {
    background: var(--button-bg-danger); /* 统一危险操作按钮颜色 */
}

/* 词库按钮样式 */
.deck-btn {
    background: var(--button-bg-deck);
    width: 100%;
    margin: 0;
    padding: 1rem;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.deck-btn:hover {
    background: linear-gradient(135deg, #4ad6ce 0%, #9d7bb9 100%); /* Keep original hover for now */
}

.deck-btn:disabled {
    background: #cccccc;
    cursor: not-allowed;
    transform: none;
}

/* 学习页面专用样式 */
#card-container {
    padding: 1rem;
    min-height: 70vh;
    opacity: 1;
    display: flex;
    flex-direction: column;
    align-items: center; /* 居中卡片 */
}

/* 进度条容器 */
#progress-container {
    width: 100%;
    max-width: 500px;
    background: var(--progress-bg);
    border-radius: 10px;
    margin: 0 auto 2rem; /* 修改外边距以实现水平居中 */
    overflow: hidden;
    box-shadow: inset 0 2px 5px rgba(0,0,0,0.1);
}

#progress-bar {
    width: 0%;
    height: 24px;
    background: var(--progress-bar-bg);
    color: white;
    text-align: center;
    line-height: 24px;
    font-weight: bold;
    font-size: 0.9rem;
}

/* 闪卡样式 */
.flashcard {
    background: var(--flashcard-bg);
    border-radius: 16px;
    padding: 2rem;
    margin: 1rem auto;
    width: 90%;
    max-width: 90%;
    box-shadow: var(--flashcard-shadow);
    border: 1px solid var(--flashcard-border);
    min-height: 250px; /* 增加最小高度 */
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    contain: content;
    flex-grow: 1; /* 允许卡片成长占据可用空间 */
    text-align: center; /* 确保卡片内文本默认居中 */
}

.flashcard:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 35px rgba(0, 0, 0, 0.2); /* 保持一致的阴影效果 */
}

/* 单词显示区域 */
#word-display {
    font-size: 2.2rem;
    font-weight: bold;
    margin-bottom: 1.5rem;
    color: var(--word-display-text);
    line-height: 1.4;
    min-height: 80px;
    display: flex;
    align-items: center;
    justify-content: center;
    width: max-content;
    max-width: 100%;
    padding: 1rem 2rem;
    background: var(--word-display-bg);
    border-radius: 12px;
    outline: 2px dashed var(--word-display-outline-color);
    outline-offset: -2px;
    margin-left: auto;
    margin-right: auto;
}

#word-display-wrapper {
    position: relative;
    width: 100%;
}

.tts-play-btn {
    position: absolute;
    top: 50%;
    right: 10px;
    transform: translateY(-50%);
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #667eea;
}

.ai-assist-btn {
    position: absolute;
    top: 10px;
    right: 50px;
    background: none;
    border: none;
    font-size: 1.2rem;
    cursor: pointer;
    color: #ffb74d; /* Orange/Gold for magic feel */
    opacity: 0.7;
    transition: opacity 0.2s;
}

.ai-assist-btn:hover {
    opacity: 1;
    transform: scale(1.1);
}

#word-display-wrapper[dir="rtl"] .tts-play-btn {
    right: auto;
    left: 10px;
}

#answer-wrapper {
    position: relative;
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* 答案和解释显示区域 */
#answer-display, #explanation-display {
    font-size: 1.8rem;
    margin: 1rem 0;
    color: var(--answer-display-text); /* 默认答案文本颜色 */
    line-height: 1.5;
    min-height: 100px;
    display: flex;
    align-items: center;
    justify-content: center; /* 确保文本内容居中 */
    width: 100%;
    padding: 1.5rem;
    border-radius: 12px;
    cursor: pointer;
    position: relative;
    overflow: hidden;
    text-align: center;
}

/* 遮挡效果 - 修复版 */
.spoiler {
    background: var(--answer-spoiler-bg) !important;
    color: transparent !important;
    user-select: none;
    position: relative;
}

.spoiler::before {
    content: "👆 点击显示";
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: var(--answer-spoiler-text);
    font-size: 1.2rem;
    font-weight: bold;
    opacity: 0.8;
}

.spoiler:hover::before {
    content: "👆 点击显示答案";
    opacity: 1;
}

.spoiler.revealed {
    background: var(--answer-display-bg) !important;
    color: var(--answer-display-text) !important;
    user-select: auto;
}

.spoiler.revealed::before {
    display: none;
}

/* 解释文本的特殊样式 */
#explanation-wrapper {
    position: relative;
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
}

#explanation-display {
    font-size: 1.4rem;
    background: var(--explanation-display-bg);
    color: var(--explanation-display-text);
    border: 1px solid var(--explanation-border);
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 1.5rem; /* 统一内边距 */
    position: relative; /* 为内部绝对定位的按钮提供容器 */
}

#explanation-display.spoiler {
    background: var(--explanation-spoiler-bg) !important;
}

#explanation-display.spoiler::before {
    content: "💡 点击显示解释";
}

#explanation-display.revealed {
    background: var(--explanation-display-bg) !important;
    color: var(--explanation-display-text) !important;
}

/* 阿拉伯语文本特殊处理 */
[dir="rtl"] {
    font-family: 'Noto Sans Arabic', 'Traditional Arabic', Arial, sans-serif;
    font-size: 2rem !important;
    font-weight: 600;
    letter-spacing: 0;
}

/* 控制按钮组容器 */
#controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    margin: 2rem 0;
    width: 100%;
    max-width: 565.33px;
}

#controls .btn {
    flex: 1; /* 允许按钮拉伸以填充容器 */
    padding: 1.2rem 0.5rem;
    font-size: 1.1rem;
    font-weight: bold;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

/* 特定按钮颜色 */
#forgot-btn {
    background: linear-gradient(135deg, #ff6b6b 0%, #ee5a52 100%);
}
#hard-btn {
    background: linear-gradient(135deg, #ffa726 0%, #fb8c00 100%);
}
#easy-btn {
    background: linear-gradient(135deg, #66bb6a 0%, #4caf50 100%);
}

#forgot-btn:hover { background: linear-gradient(135deg, #ff5252 0%, #e53935 100%); }
#hard-btn:hover { background: linear-gradient(135deg, #ff9800 0%, #f57c00 100%); }
#easy-btn:hover { background: linear-gradient(135deg, #4caf50 0%, #43a047 100%); }


/* 导航控制按钮 */
#nav-controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-top: 1rem;
    width: 100%;
    max-width: 500px;
}

#nav-controls .btn {
    flex: 1;
    max-width: 150px;
    padding: 0.8rem;
    background: linear-gradient(135deg, #a8edea, #fed6e3);
    color: #333;
    font-weight: 600;
}

/* 响应式调整 */
@media (max-width: 480px) {
    #card-container {
        padding: 1rem 0.5rem;
    }

    .flashcard {
        padding: 1.5rem;
        min-height: 180px;
    }

    #word-display {
        font-size: 1.8rem;
        min-height: 70px;
    }

    #answer-display, #explanation-display {
        font-size: 1.5rem;
        min-height: 80px;
        padding: 1rem;
    }

    [dir="rtl"] {
        font-size: 1.7rem !important;
    }

    #controls .btn {
        min-width: 80px;
        padding: 1rem 0.3rem;
        font-size: 1rem;
    }
}

/* 确保学习页面内容正确显示 */
#study-page .page-content {
    padding: 0;
    height: 100%;
}

/* 模态框样式 */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    display: none; /* 默认隐藏 */
    z-index: 2000;
}

.modal.visible {
    display: block; /* 当模态框可见时，显示它 */
}

.modal-content {
    position: absolute;
    top: auto;
    left: 50%;
    transform: translate(-50%, 10%);
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    max-width: 90%;
    width: 500px;
    max-height: 80vh;
    overflow-y: auto;
    contain: content;
    text-align: center; /* 使模态框内容居中 */
}

/* 闪卡出现动画 */
@keyframes cardAppear {
    0% {
        transform: translateY(20px);
        opacity: 0;
        box-shadow: none;
    }
    100% {
        transform: translateY(0);
        opacity: 1;
        box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
    }
}

/* -------------- 新增/修改的 UI 优化样式 -------------- */

/* 统一 Section 容器样式 (卡片化) */
.settings-section,
.feature-section {
    background-color: #ffffff;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
    border-left: 5px solid #667eea; /* 强调色左边框 */
}

.settings-section:hover,
.feature-section:hover {
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.1);
}

.settings-section h3,
.feature-section h3 {
    color: #2d3748;
    margin-top: 0;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid #f0f2f5;
    font-size: 1.2rem;
}

/* 词库选择容器 */
#deck-selection-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
}

/* 导入区域优化 */
.import-divider {
    height: 1px;
    background-color: #e0e6ed;
    margin: 1.5rem 0;
}

.import-info {
    margin-top: 1rem;
    padding: 0.75rem;
    background-color: #f7f9fc;
    border-radius: 8px;
    border: 1px solid #e0e6ed;
}

.format-example {
    background-color: #e8eaf6;
    color: #3f51b5;
    padding: 1rem;
    margin-top: 0.5rem;
    border-radius: 6px;
    font-family: monospace;
    white-space: pre-wrap;
    font-size: 0.8rem; /* 稍微缩小字体以提高代码可读性 */
    overflow-x: auto;
    line-height: 1.3;
}
.format-example details {
    margin-top: 0.5rem;
}

/* 学习模式按钮组 (Segmented Controls) */
#mode-selection-container {
    display: flex;
    justify-content: space-between;
    background-color: #e9ecef;
    border-radius: 8px;
    padding: 4px;
    box-sizing: border-box;
}

#mode-selection-container label {
    flex: 1;
    text-align: center;
    padding: 0; /* 移除 label 上的 padding */
    cursor: pointer;
    font-weight: 600;
    color: #495057;
    border-radius: 6px;
    position: relative;
}

#mode-selection-container input[type="radio"] {
    display: none;
}

.radio-label {
    display: block;
    width: 100%;
    height: 100%;
    border-radius: 6px;
    padding: 0.6rem 0.5rem; /* 将 padding 移到 span 上 */
    box-sizing: border-box;
}

#mode-selection-container input[type="radio"]:checked + .radio-label {
    background-color: white;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    color: #667eea;
}

/* 数据管理按钮布局 (Grid) */
.settings-buttons {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
    margin-top: 1rem;
}

.settings-buttons .settings-btn {
    width: auto;
    margin: 0;
    display: flex;
    align-items: center;
    justify-content: flex-start;
    gap: 0.5rem;
    font-size: 0.95rem;
    padding: 0.8rem 1rem;
}

.settings-buttons .settings-btn i {
    font-size: 1.1rem;
}

/* 应用信息链接优化 */
.update-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: #667eea;
    font-weight: 600;
    padding: 0.5rem 0;
}
.update-link:hover {
    text-decoration: underline;
}

/* 模态框按钮 */
.modal-content .btn {
    margin: 0.3rem;
}

/* 完成屏幕样式 */
#completion-screen {
    text-align: center;
    padding: 3rem 1rem;
    background: linear-gradient(145deg, #e6fffa 0%, #b2ebf2 100%);
    border-radius: 16px;
    margin-top: 2rem;
    box-shadow: 0 8px 20px rgba(0, 150, 136, 0.2);
    display: none; /* 默认隐藏，通过 JS 控制显示 */
}

#completion-screen h2 {
    color: #00897b;
    font-size: 2rem;
    margin-bottom: 1rem;
}

#completion-screen p {
    color: #00695c;
    font-size: 1.1rem;
    margin-bottom: 2rem;
}

#completion-screen #finish-back-to-menu-btn {
    background: linear-gradient(135deg, #00897b, #004d40) !important;
    color: white;
    font-weight: bold;
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

@keyframes bounceIn {
    0% { transform: scale(0.8); opacity: 0; }
    50% { transform: scale(1.05); opacity: 1; }
    100% { transform: scale(1); }
}

/* 统计模态框样式 */
#stats-modal .modal-content {
    text-align: left;
}

#stats-modal-title {
    margin-top: 0;
    color: #2d3748;
    border-bottom: 2px solid #667eea;
    padding-bottom: 0.5rem;
    margin-bottom: 1rem;
}

#stats-modal-body {
    background-color: #f7f9fc;
    padding: 1rem;
    border-radius: 8px;
    border: 1px solid #e0e6ed;
    max-height: 60vh;
    overflow-y: auto;
    line-height: 1.6;
    color: #4a5568;
}

/* 统计模态框中的分类样式 */
.stats-category {
    margin-bottom: 1.5rem;
}

.stats-category:last-child {
    margin-bottom: 0;
}

.stats-category h3 {
    font-size: 1.1rem;
    color: #764ba2;
    margin-bottom: 0.8rem;
    padding-bottom: 0.4rem;
    border-bottom: 1px solid #e0e6ed;
}

.stats-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.stats-item {
    display: flex;
    justify-content: space-between;
    padding: 0.6rem 0;
    border-bottom: 1px solid #f0f2f5;
}

.stats-item:last-child {
    border-bottom: none;
}

.stats-label {
    font-weight: 600;
    color: #4a5568;
}

.stats-value {
    font-weight: bold;
    color: #667eea;
}

#stats-modal-close-btn {
    margin-top: 1.5rem;
    width: 100%;
    background: linear-gradient(135deg, #667eea, #764ba2);
}

/* 主动回忆遮罩 */
.recall-overlay {
    position: absolute;
    top: 0;
    left: -10%;
    width: 120%;
    height: 140%;
    background-color: rgba(0, 0, 0, 0.7);
    color: white;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border-radius: 12px;
    z-index: 10;
}

.recall-overlay p {
    font-size: 1.2rem;
    margin-top: 1rem;
}

.recall-circle-timer {
    width: 80px;
    height: 80px;
    position: relative;
}

.timer-svg {
    transform: rotate(-90deg);
}

.timer-bg {
    fill: none;
    stroke: #fff;
    stroke-width: 10;
}

.timer-progress {
    fill: none;
    stroke: #667eea;
    stroke-width: 10;
    stroke-dasharray: 283; /* 2 * PI * 45 */
    stroke-dashoffset: 283;
}

.timer-countdown {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 2rem;
    font-weight: bold;
    color: white;
}

@keyframes countdown {
    from {
        stroke-dashoffset: 0;
    }
    to {
        stroke-dashoffset: 283;
    }
}

/* 主动回忆设置 */
#recall-setting-container {
    display: flex;
    align-items: center;
}

#recall-setting-container label {
    display: flex;
    align-items: center;
    cursor: pointer;
}

#recall-setting {
    margin-right: 0.5rem;
}

.setting-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.5rem 0;
}

/* 夜间模式样式 */
body.theme-night {
    --primary-color: #8a9ff0;
    --primary-color-dark: #6a7fde;
    --primary-color-light: #3a3a3a;
    --secondary-color: #f093fb; /* Keep original for now */
    --secondary-color-dark: #f5576c; /* Keep original for now */

    --text-color: #e0e0e0;
    --text-color-secondary: #a0a0a0;
    --text-color-light: #666;

    --background-color: #1a1a1a;
    --background-color-light: #2c2c2c;
    --background-color-dark: #3a3a3a;

    --border-color: #444;
    --shadow-color: rgba(0, 0, 0, 0.4);
    --hover-color: #3a3a3a;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, var(--background-color-dark), #4a4a4a);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #666;

    --answer-display-bg: linear-gradient(135deg, #4c5a7a, #5c6a8a);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #4a4a4a, #5a5a5a);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #4a4a4a, #5a5a5a);
    --explanation-display-text: #d0d0d0;
    --explanation-border: #666;
    --explanation-spoiler-bg: linear-gradient(135deg, #5a5a5a, #6a6a6a);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--primary-color), var(--primary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); /* Keep original for now */
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); /* Keep original for now */
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%); /* Keep original for now */
    --button-bg-danger: linear-gradient(135deg, #f44336 0%, #b71c1c 100%); /* Keep original for now */
    --button-text-light: #1a1a1a;
    --button-text-dark: white;
}

 .theme-night .bottom-nav {
    background: var(--background-color-light);
    box-shadow: 0 -4px 12px var(--shadow-color);
}

 .theme-night .nav-btn {
    color: var(--text-color-secondary);
}

 .theme-night .nav-btn.active {
    color: var(--primary-color);
}

 .theme-night .nav-btn.active::after {
    background-color: var(--primary-color);
}

 .theme-night .settings-section,
 .theme-night .feature-section {
    background-color: var(--background-color-light);
    border-left: 5px solid var(--primary-color);
}

 .theme-night .settings-section h3,
 .theme-night .feature-section h3 {
    color: var(--text-color);
    border-bottom: 1px solid var(--border-color);
}

 .theme-night #mode-selection-container {
    background-color: var(--border-color);
}

 .theme-night #mode-selection-container label {
    color: var(--text-color-secondary);
}

 .theme-night #mode-selection-container input[type="radio"]:checked + .radio-label {
    background-color: #555; /* Specific for radio checked */
    color: var(--primary-color);
}

 .theme-night .tts-play-btn {
    color: var(--primary-color);
}

 .theme-night .btn {
    background: var(--button-bg-primary);
    color: var(--button-text-light);
}

 .theme-night .feature-btn {
    background: var(--button-bg-feature);
    color: var(--button-text-dark);
}

 .theme-night .settings-btn {
    background: var(--button-bg-settings);
    color: var(--button-text-dark);
}

 .theme-night .settings-btn.danger {
    background: var(--button-bg-danger);
    color: var(--button-text-dark);
}

 .theme-night .deck-btn {
    background: var(--button-bg-deck);
    color: var(--button-text-light);
}

 .theme-night #forgot-btn {
    background: linear-gradient(135deg, #ff6b6b 0%, #ee5a52 100%); /* Specific for forgot */
    color: white;
}
 .theme-night #hard-btn {
    background: linear-gradient(135deg, #ffa726 0%, #fb8c00 100%); /* Specific for hard */
    color: white;
}
 .theme-night #easy-btn {
    background: linear-gradient(135deg, #66bb6a 0%, #4caf50 100%); /* Specific for easy */
    color: white;
}

 .theme-night #nav-controls .btn {
    background: linear-gradient(135deg, #a8edea, #fed6e3); /* Specific for nav controls */
    color: #333;
}

 .theme-night .modal-content {
    background: var(--background-color-light);
    color: var(--text-color);
}

 .theme-night #stats-modal-title {
    color: var(--text-color);
    border-bottom: 2px solid var(--primary-color);
}

 .theme-night #stats-modal-body {
    background-color: var(--background-color-dark);
    border: 1px solid #555;
    color: var(--text-color);
}

 .theme-night .stats-category h3 {
    color: var(--primary-color);
    border-bottom: 1px solid var(--border-color);
}

 .theme-night .stats-item {
    border-bottom: 1px solid var(--border-color);
}

 .theme-night .stats-label {
    color: var(--text-color);
}

 .theme-night .stats-value {
    color: var(--primary-color);
}

 .theme-night #stats-modal-close-btn {
    background: var(--button-bg-primary);
    color: var(--button-text-light);
}

 .theme-night .import-info {
    background-color: var(--background-color-dark);
    border: 1px solid #555;
}

 .theme-night .format-example {
    background-color: #4a4a4a;
    color: #b490ca;
}

 .theme-night #progress-container {
    background: var(--border-color);
}

 .theme-night #progress-bar {
    background: var(--progress-bar-bg);
}

/* 开关样式 */
.switch {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 34px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #ccc;
}

.slider:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
    background-color: white;
}

input:checked + .slider {
    background-color: #8a9ff0;
}

input:focus + .slider {
    box-shadow: 0 0 1px #8a9ff0;
}

input:checked + .slider:before {
    -webkit-transform: translateX(26px);
    -ms-transform: translateX(26px);
    transform: translateX(26px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

/* 数据清除模态框样式 */
#clear-data-modal .modal-content {
    text-align: left;
}

#clear-data-modal h2 {
    color: #db1818;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

#clear-data-form {
    margin-top: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.checkbox-container {
    display: block;
    position: relative;
    padding-left: 35px;
    cursor: pointer;
    font-size: 1.1rem;
    user-select: none;
    background-color: #f7f9fc;
    padding: 1rem 1rem 1rem 35px;
    border-radius: 8px;
    border: 1px solid #e0e6ed;
}

 .theme-night .checkbox-container {
    background-color: #3a3a3a;
    border-color: #555;
}

.checkbox-container input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
    height: 0;
    width: 0;
}

.checkmark {
    position: absolute;
    top: 50%;
    left: 10px;
    transform: translateY(-50%);
    height: 22px;
    width: 22px;
    background-color: #eee;
    border: 1px solid #ccc;
    border-radius: 4px;
}

 .theme-night .checkmark {
    background-color: #555;
    border-color: #777;
}

.checkbox-container:hover input ~ .checkmark {
    background-color: #ccc;
}

.checkbox-container input:checked ~ .checkmark {
    background-color: #d32f2f;
}

.checkmark:after {
    content: "";
    position: absolute;
    display: none;
}

.checkbox-container input:checked ~ .checkmark:after {
    display: block;
}

.checkbox-container .checkmark:after {
    left: 7px;
    top: 3px;
    width: 5px;
    height: 10px;
    border: solid white;
    border-width: 0 3px 3px 0;
    transform: rotate(45deg);
}

.checkbox-container small {
    display: block;
    font-size: 0.85rem;
    color: #666;
    margin-top: 4px;
}

 .theme-night .checkbox-container small {
    color: #a0a0a0;
}

#clear-data-modal .modal-footer {
    margin-top: 2rem;
    text-align: right;
}

#execute-clear-data-btn {
    background: linear-gradient(135deg, #f44336 0%, #b71c1c 100%);
}



/* 在线导入模态框样式 */
#import-modal .modal-content {
    max-width: 500px;
    width: 90%;
    text-align: center;
    position: relative;
}

#import-modal .close-button {
    position: absolute;
    top: 15px;
    right: 20px;
    font-size: 2rem;
    color: #aaa;
    cursor: pointer;
}

#import-modal .close-button:hover {
    color: #333;
}

 .theme-night #import-modal .close-button:hover {
    color: #fff;
}

#import-modal h2 {
    margin-top: 0;
    color: #2d3748;
}

 .theme-night #import-modal h2 {
    color: #e0e0e0;
}

.modal-subtitle {
    font-size: 0.9rem;
    color: #666;
    margin-top: -1rem;
    margin-bottom: 1.5rem;
}

 .theme-night .modal-subtitle {
    color: #a0a0a0;
}

#online-lexicon-list {
    max-height: 50vh;
    overflow-y: auto;
    margin-bottom: 1.5rem;
    text-align: left;
    border-top: 1px solid #eee;
    border-bottom: 1px solid #eee;
    padding: 10px 0;
}

 .theme-night #online-lexicon-list {
    border-color: #444;
}

.online-lexicon-item {
    padding: 1rem 1.5rem;
    background-color: #f7f9fc;
    border-radius: 8px;
    margin: 0.5rem 0;
    cursor: pointer;
    font-weight: 600;
    color: #4a5568;
}

.online-lexicon-item:hover {
    background-color: #e9ecef;
    transform: translateX(5px);
}

 .theme-night .online-lexicon-item {
    background-color: #3a3a3a;
    color: #d0d0d0;
}

 .theme-night .online-lexicon-item:hover {
    background-color: #4a4a4a;
}

#import-modal .modal-footer {
    margin-top: 1rem;
}

#import-local-lexicon-btn {
    background: linear-gradient(135deg, #6c757d 0%, #495057 100%);
}

/* 一词多义切换按钮样式 */
#definition-toggle-container {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.definition-toggle-btn {
    background-color: #e9ecef;
    color: #495057;
    border: 1px solid #dee2e6;
    padding: 0.4rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
}

.definition-toggle-btn:hover {
    background-color: #dee2e6;
}

.definition-toggle-btn.active {
    background-color: #667eea;
    color: white;
    border-color: #667eea;
    box-shadow: 0 2px 5px rgba(102, 126, 234, 0.4);
}

 .theme-night .definition-toggle-btn {
    background-color: #4a4a4a;
    color: #d0d0d0;
    border-color: #666;
}

 .theme-night .definition-toggle-btn:hover {
    background-color: #5a5a5a;
}



 .theme-night .definition-toggle-btn.active {

    background-color: #8a9ff0;

    color: #1a1a1a;

    border-color: #8a9ff0;

}



/* 新增：模态框通用操作按钮容器 */

.modal-actions {

    display: flex;

    justify-content: center;

    gap: 1rem;

    margin-top: 1.5rem;

}



/* 新增：拒绝/次要操作按钮样式 */

.btn.btn-secondary {

    background: #6c757d;

    box-shadow: none;

}



 .theme-night .btn.btn-secondary {

    background: #5a5a5a;

    color: #e0e0e0;

}

/* 新增：骨架屏加载样式 */
.skeleton-loader {
    display: none; /* 默认隐藏 */
    padding: 1.5rem;
}

.skeleton-item {
    background-color: #e0e0e0;
    border-radius: 8px;
    margin-bottom: 1rem;
    height: 60px;
    opacity: 0.6;
}

 .theme-night .skeleton-item {
    background-color: #3a3a3a;
}

@keyframes pulse {
    0% {
        opacity: 0.6;
    }
    50% {
        opacity: 1;
    }
    100% {
        opacity: 0.6;
    }
}

@media (prefers-reduced-motion: no-preference) {
    .page.active {
        animation: fadeIn 0.3s ease-in;
    }
    .import-message {
        animation: fadeInDown 0.5s;
    }
    #completion-screen {
        animation: bounceIn 0.5s ease-out;
    }
    .timer-progress {
        animation: countdown 5s linear forwards;
    }
    .skeleton-item {
        animation: pulse 1.5s infinite ease-in-out;
    }
    .nav-btn {
        transition: all 0.3s ease;
    }
    .btn {
        transition: all 0.3s ease;
    }
    .btn:active {
        transition: transform 0.1s ease;
    }
    #progress-bar {
        transition: width 0.5s ease;
    }
    .flashcard {
        transition: transform 0.3s ease, box-shadow 0.3s ease;
    }
    #answer-display, #explanation-display {
        transition: all 0.3s ease;
    }
    .settings-section, .feature-section {
        transition: box-shadow 0.3s ease;
    }
    #mode-selection-container label {
        transition: all 0.2s ease;
    }
    #import-modal .close-button {
        transition: color 0.2s;
    }
    .online-lexicon-item {
        transition: background-color 0.2s, transform 0.2s;
    }
    .definition-toggle-btn {
        transition: all 0.2s ease;
    }
    .slider {
        transition: .4s;
    }
    .slider:before {
        transition: .4s;
    }
}

/* 主题选择下拉框样式 */
.theme-select {
    padding: 0.5rem;
    border-radius: 8px;
    border: 1px solid #ccc;
    background-color: white;
    min-width: 120px;
    font-size: 1rem;
}

 .theme-night .theme-select {
    background-color: #444;
    color: #e0e0e0;
    border-color: #666;
}

/* 金日主题 */
body.theme-golden-sun {
    --primary-color: #ff8f00;
    --primary-color-dark: #ffa000;
    --primary-color-light: #ffecb3;
    --secondary-color: #ffb300;
    --secondary-color-dark: #ffa000;

    --text-color: #4e342e;
    --text-color-secondary: #8d6e63;
    --text-color-light: #a1887f;

    --background-color: #fff8e1;
    --background-color-light: #fffde7;
    --background-color-dark: #fff1cf;

    --border-color: #ffecb3;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --hover-color: #fff3e0;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, #fff9c4, #ffecb3);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #ffab00;

    --answer-display-bg: linear-gradient(135deg, #fff9c4, #ffecb3);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #a1887f, #795548);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #fff3e0, #ffe0b2);
    --explanation-display-text: #e65100;
    --explanation-border: #ffb74d;
    --explanation-spoiler-bg: linear-gradient(135deg, #5d4037, #795548);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--primary-color), var(--primary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); /* Keep original for now */
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); /* Keep original for now */
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%); /* Keep original for now */
    --button-bg-danger: linear-gradient(135deg, #4e342e, #3e2723);
    --button-text-light: var(--text-color);
    --button-text-dark: #fff8e1;
}
.theme-golden-sun .bottom-nav { background: var(--background-color-dark); }
.theme-golden-sun .nav-btn { color: var(--text-color-secondary); }
.theme-golden-sun .nav-btn.active { color: var(--primary-color); }
.theme-golden-sun .nav-btn.active::after { background-color: var(--primary-color); }
.theme-golden-sun .settings-section, .theme-golden-sun .feature-section { background-color: var(--background-color-light); border-left-color: #ffab00; }
.theme-golden-sun .settings-section h3, .theme-golden-sun .feature-section h3 { color: var(--text-color); border-bottom-color: var(--background-color-dark); }
.theme-golden-sun .modal-content { background: var(--background-color-light); }
.theme-golden-sun .btn { background: var(--button-bg-primary); color: var(--button-text-light); }
.theme-golden-sun .settings-btn.danger { background: var(--button-bg-danger); color: var(--button-text-dark); }
.theme-golden-sun .spoiler.revealed { background: var(--answer-display-bg) !important; color: var(--answer-display-text) !important; }

/* 樱粉主题 */
body.theme-sakura-pink {
    --primary-color: #f06292;
    --primary-color-dark: #f06292;
    --primary-color-light: #f8bbd0;
    --secondary-color: #f48fb1;
    --secondary-color-dark: #f06292;

    --text-color: #5b3f4f;
    --text-color-secondary: #886578;
    --text-color-light: #b0a0a8;

    --background-color: #fff0f5;
    --background-color-light: #fff5f7;
    --background-color-dark: #fff5f7;

    --border-color: #ffdde1;
    --shadow-color: rgba(0, 0, 0, 0.08); /* Lighter shadow for pastel theme */
    --hover-color: #ffeef2;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, #fce4ec, #f8bbd0);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #f06292;

    --answer-display-bg: linear-gradient(135deg, #fce4ec, #f8bbd0);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #886578, #5b3f4f);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #fff0f5, #ffe0e9);
    --explanation-display-text: #c2185b;
    --explanation-border: #f48fb1;
    --explanation-spoiler-bg: linear-gradient(135deg, #5b3f4f, #4a323f);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); /* Keep original for now */
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); /* Keep original for now */
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%); /* Keep original for now */
    --button-bg-danger: linear-gradient(135deg, #5b3f4f, #4a323f);
    --button-text-light: var(--text-color);
    --button-text-dark: #fff0f5;
}
.theme-sakura-pink .bottom-nav { background: var(--background-color-dark); }
.theme-sakura-pink .nav-btn { color: var(--text-color-secondary); }
.theme-sakura-pink .nav-btn.active { color: var(--primary-color); }
.theme-sakura-pink .nav-btn.active::after { background-color: var(--primary-color); }
.theme-sakura-pink .settings-section, .theme-sakura-pink .feature-section { background-color: var(--background-color-light); border-left-color: var(--primary-color-light); }
.theme-sakura-pink .settings-section h3, .theme-sakura-pink .feature-section h3 { color: var(--text-color); border-bottom-color: var(--background-color-dark); }
.theme-sakura-pink .modal-content { background: var(--background-color-light); }
.theme-sakura-pink .btn { background: var(--button-bg-primary); color: var(--button-text-light); }
.theme-sakura-pink .settings-btn.danger { background: var(--button-bg-danger); color: var(--button-text-dark); }
.theme-sakura-pink .spoiler.revealed { background: var(--answer-display-bg) !important; color: var(--answer-display-text) !important; }

/* 苔绿主题 */
body.theme-moss-green {
    --primary-color: #7cb342;
    --primary-color-dark: #8bc34a;
    --primary-color-light: #aed581;
    --secondary-color: #9ccc65;
    --secondary-color-dark: #8bc34a;

    --text-color: #33691e;
    --text-color-secondary: #558b2f;
    --text-color-light: #7cb342;

    --background-color: #f1f8e9;
    --background-color-light: #f9fff6;
    --background-color-dark: #f9fff6;

    --border-color: #dcedc8;
    --shadow-color: rgba(0, 0, 0, 0.08);
    --hover-color: #e8f5e9;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, #dcedc8, #c5e1a5);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #aed581;

    --answer-display-bg: linear-gradient(135deg, #dcedc8, #c5e1a5);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #558b2f, #33691e);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #f1f8e9, #e6ee9c);
    --explanation-display-text: #689f38;
    --explanation-border: #aed581;
    --explanation-spoiler-bg: linear-gradient(135deg, #33691e, #1b5e20);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); /* Keep original for now */
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); /* Keep original for now */
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%); /* Keep original for now */
    --button-bg-danger: linear-gradient(135deg, #f1f8e9, #dcedc8);
    --button-text-light: var(--text-color);
    --button-text-dark: #33691e;
}
.theme-moss-green .bottom-nav { background: var(--background-color-dark); }
.theme-moss-green .nav-btn { color: var(--text-color-secondary); }
.theme-moss-green .nav-btn.active { color: var(--primary-color); }
.theme-moss-green .nav-btn.active::after { background-color: var(--primary-color); }
.theme-moss-green .settings-section, .theme-moss-green .feature-section { background-color: var(--background-color-light); border-left-color: var(--primary-color-light); }
.theme-moss-green .settings-section h3, .theme-moss-green .feature-section h3 { color: var(--text-color); border-bottom-color: var(--background-color-dark); }
.theme-moss-green .modal-content { background: var(--background-color-light); }
.theme-moss-green .btn { background: var(--button-bg-primary); color: var(--button-text-light); }
.theme-moss-green .settings-btn.danger { background: var(--button-bg-danger); color: var(--button-text-dark); }
.theme-moss-green .spoiler.revealed { background: var(--answer-display-bg) !important; color: var(--answer-display-text) !important; }

/* 堇紫主题 */
body.theme-violet {
    --primary-color: #ab47bc;
    --primary-color-dark: #ba68c8;
    --primary-color-light: #ce93d8;
    --secondary-color: #ba68c8;
    --secondary-color-dark: #ab47bc;

    --text-color: #4a148c;
    --text-color-secondary: #6a1b9a;
    --text-color-light: #9c27b0;

    --background-color: #f3e5f5;
    --background-color-light: #faf5ff;
    --background-color-dark: #faf5ff;

    --border-color: #e1bee7;
    --shadow-color: rgba(0, 0, 0, 0.08);
    --hover-color: #f8eaf9;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, #e1bee7, #d1c4e9);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #ce93d8;

    --answer-display-bg: linear-gradient(135deg, #e1bee7, #d1c4e9);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #6a1b9a, #4a148c);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #f3e5f5, #ede7f6);
    --explanation-display-text: #8e24aa;
    --explanation-border: #ce93d8;
    --explanation-spoiler-bg: linear-gradient(135deg, #4a148c, #311b92);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); /* Keep original for now */
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); /* Keep original for now */
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%); /* Keep original for now */
    --button-bg-danger: linear-gradient(135deg, #f3e5f5, #e1bee7);
    --button-text-light: var(--text-color);
    --button-text-dark: #4a148c;
}
.theme-violet .bottom-nav { background: var(--background-color-dark); }
.theme-violet .nav-btn { color: var(--text-color-secondary); }
.theme-violet .nav-btn.active { color: var(--primary-color); }
.theme-violet .nav-btn.active::after { background-color: var(--primary-color); }
.theme-violet .settings-section, .theme-violet .feature-section { background-color: var(--background-color-light); border-left-color: var(--primary-color-light); }
.theme-violet .settings-section h3, .theme-violet .feature-section h3 { color: var(--text-color); border-bottom-color: var(--background-color-dark); }
.theme-violet .modal-content { background: var(--background-color-light); }
.theme-violet .btn { background: var(--button-bg-primary); color: var(--button-text-light); }
.theme-violet .settings-btn.danger { background: var(--button-bg-danger); color: var(--button-text-dark); }
.theme-violet .spoiler.revealed { background: var(--answer-display-bg) !important; color: var(--answer-display-text) !important; }

/* 赤红主题 */
body.theme-crimson-red {
    --primary-color: #e53935;
    --primary-color-dark: #ef5350;
    --primary-color-light: #ffcdd2;
    --secondary-color: #ef5350;
    --secondary-color-dark: #e53935;

    --text-color: #b71c1c;
    --text-color-secondary: #c62828;
    --text-color-light: #e0e0e0;

    --background-color: #ffebee;
    --background-color-light: #fff5f5;
    --background-color-dark: #fff5f5;

    --border-color: #ffcdd2;
    --shadow-color: rgba(0, 0, 0, 0.08);
    --hover-color: #ffeeee;

    --flashcard-bg: var(--background-color-light);
    --flashcard-border: var(--border-color);
    --flashcard-shadow: 0 8px 25px var(--shadow-color);

    --word-display-bg: linear-gradient(135deg, #ffcdd2, #ef9a9a);
    --word-display-text: var(--text-color);
    --word-display-outline-color: #ef9a9a;

    --answer-display-bg: linear-gradient(135deg, #ffcdd2, #ef9a9a);
    --answer-display-text: var(--text-color);
    --answer-spoiler-bg: linear-gradient(135deg, #c62828, #b71c1c);
    --answer-spoiler-text: white;

    --explanation-display-bg: linear-gradient(135deg, #ffebee, #ffdddd);
    --explanation-display-text: #d32f2f;
    --explanation-border: #ef9a9a;
    --explanation-spoiler-bg: linear-gradient(135deg, #b71c1c, #9e0c0c);
    --explanation-spoiler-text: white;

    --progress-bg: var(--border-color);
    --progress-bar-bg: linear-gradient(90deg, var(--primary-color), var(--primary-color-dark));

    --button-bg-primary: linear-gradient(135deg, var(--secondary-color), var(--secondary-color-dark));
    --button-bg-feature: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --button-bg-settings: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --button-bg-deck: linear-gradient(135deg, #5ee7df 0%, #b490ca 100%);
    --button-bg-danger: linear-gradient(135deg, #0595f5 0%, #3189fb 100%);
    --button-text-light: var(--background-color);
    --button-text-dark: #bff803;
}
.theme-crimson-red .bottom-nav { background: var(--background-color-dark); }
.theme-crimson-red .nav-btn { color: var(--text-color-secondary); }
.theme-crimson-red .nav-btn.active { color: var(--primary-color); }
.theme-crimson-red .nav-btn.active::after { background-color: var(--primary-color); }
.theme-crimson-red .settings-section, .theme-crimson-red .feature-section { background-color: var(--background-color-light); border-left-color: var(--primary-color-light); }
.theme-crimson-red .settings-section h3, .theme-crimson-red .feature-section h3 { color: var(--text-color); border-bottom-color: var(--background-color-dark); }
.theme-crimson-red .modal-content { background: var(--background-color-light); }
.theme-crimson-red .btn { background: var(--button-bg-primary); color: var(--button-text-light); }
.theme-crimson-red .settings-btn.danger { background: var(--button-bg-danger); color: var(--button-text-dark); }
.theme-crimson-red .spoiler.revealed { background: var(--answer-display-bg) !important; color: var(--answer-display-text) !important; }


/* --- 规律学习范围选择模态框 --- */
.study-scope-tabs {
    display: flex;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.tab-btn {
    padding: 0.8rem 1.2rem;
    cursor: pointer;
    background-color: transparent;
    border: none;
    border-bottom: 3px solid transparent;
    font-size: 1rem;
    color: var(--text-color-secondary);
    transition: all 0.2s ease-in-out;
}

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

.tab-btn.active {
    color: var(--primary-color);
    border-bottom: 3px solid var(--primary-color);
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

.tab-content.active {
    display: block;
}

.study-scope-description {
    color: var(--text-color-secondary);
    font-size: 0.95rem;
    text-align: center;
    padding: 2rem 0;
}

.options-list {
    max-height: 40vh;
    overflow-y: auto;
    padding-right: 0.5rem; /* For scrollbar spacing */
}

.study-scope-option {
    display: block;
    padding: 0.8rem 1rem;
    margin-bottom: 0.5rem;
    background-color: var(--background-color-light);
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.study-scope-option:hover {
    background-color: var(--hover-color);
}

.study-scope-option input[type=checkbox] {
    margin-right: 0.8rem;
}

.study-scope-collection-group {
    margin-bottom: 1.5rem;
}

.study-scope-collection-group h4 {
    margin-bottom: 0.8rem;
    color: var(--primary-color);
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border-color);
}

.study-scope-deck-list {
    padding-left: 1rem;
}

.secondary-btn {
    background: var(--secondary-button-color);
    color: var(--secondary-button-text-color);
    margin-top: 10px;
}

.study-plan-display {
    margin-top: 15px;
    padding: 10px;
    background-color: var(--background-color);
    border-radius: 8px;
    color: var(--text-color-secondary);
    font-size: 0.9em;
}

#study-plan-modal .modal-content {
    max-height: 70vh;
    overflow-y: auto;
}

#study-plan-options-container {
    text-align: left;
    margin-top: 20px;
}

.study-plan-option {
    display: block;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    margin-bottom: 10px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.study-plan-option:hover {
    background-color: var(--hover-color);
}

.study-plan-collection-group {
    margin-top: 15px;
    padding-left: 15px;
    border-left: 2px solid var(--primary-color);
}

.study-plan-deck-list {
    margin-top: 10px;
    padding-left: 20px;
}

/* Mistake Notebook Styles */
.mistake-notebook-container {
    background-color: #fff0f0; /* Light red background */
}

.theme-night .mistake-notebook-container {
    background-color: #3e2723; /* Darker red/brown for night mode */
    border-color: #e57373 !important;
}

.study-mistake-btn {
    background: linear-gradient(135deg, #ef5350, #c62828);
    color: white;
}

.manage-deck-btn {
    background: #e0e0e0;
    color: #333;
    width: 40px; /* Fixed width for icon button */
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-night .manage-deck-btn {
    background: #555;
    color: #fff;
}

/* Large Modal for Word Browser */
.large-modal {
    width: 800px; /* Wider than standard modal */
    max-width: 95%;
    height: 80vh; /* Taller */
    display: flex;
    flex-direction: column;
}

.scrollable-list {
    flex-grow: 1;
    overflow-y: auto;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 10px;
    background: var(--background-color);
}

/* Word Item in Browser */
.word-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
    border-bottom: 1px solid var(--border-color);
    background: var(--background-color-light);
}

.word-item:last-child {
    border-bottom: none;
}

.word-info {
    text-align: left;
    flex-grow: 1;
}

.word-arabic {
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-right: 10px;
}

.word-chinese {
    color: var(--text-color-secondary);
    font-size: 0.95rem;
}

.word-actions {
    display: flex;
    gap: 10px;
    align-items: center;
}

.add-mistake-btn {
    background: transparent;
    border: 1px solid #ccc;
    color: #ccc;
    cursor: pointer;
    padding: 5px 10px;
    border-radius: 20px;
    transition: all 0.2s;
}

.add-mistake-btn:hover {
    border-color: #888;
    color: #888;
}

.add-mistake-btn.added {
    background: #ffebee;
    border-color: #e57373;
    color: #e57373;
}

.add-mistake-btn.added:hover {
    background: #ffcdd2;
}

.theme-night .add-mistake-btn.added {
    background: #3e2723;
    border-color: #ef5350;
    color: #ef5350;
}