/* ==========================================================================
   Card Styles - 卡片样式模块 (v4.6 - 新增例句焦点模式)
   ========================================================================== */

/* --- 组件: 3D 翻转卡片 (核心与通用) --- */
.card {
    background-color: transparent;
    height: 400px;
    perspective: 1000px;
    cursor: pointer;
    transition: all 0.35s ease-in-out;
    animation: card-fade-in 0.5s ease-out forwards;
    touch-action: pan-x;
    -webkit-tap-highlight-color: transparent;
}

.card.is-pending-removal {
    transform: scale(0.9);
    opacity: 0;
    max-height: 0;
    padding-top: 0;
    padding-bottom: 0;
    margin-bottom: -2rem;
    display: none;
    border-width: 0;
    pointer-events: none;
}

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

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s cubic-bezier(0.4, 0.2, 0.2, 1), background-color 0.3s ease, box-shadow 0.3s ease;
    transform-style: preserve-3d;
    box-shadow: var(--shadow);
    border-radius: var(--radius-lg);
}
.card.is-flipped .card-inner {
    transform: rotateY(180deg);
}
.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    background: var(--card-bg);
    border: 2px solid transparent;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}


/* --- 组件: 单词卡片正面 --- */
.card-front {
    justify-content: space-between;
    padding: 2rem 1.5rem;
    border-color: color-mix(in srgb, var(--theme-color) 40%, transparent);
}

.prefix-badge {
    position: absolute;
    top: 1rem;
    left: 1rem;
    font-size: 0.8rem;
    font-weight: bold;
    padding: 2px 8px;
    border-radius: 4px;
    text-transform: uppercase;
    opacity: 0.8;
    color: var(--theme-color);
    background: color-mix(in srgb, var(--theme-color) 10%, transparent);
}

.visual-area {
    flex-grow: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}
.visual-area svg {
    width: 120px;
    height: 120px;
    transition: transform 0.3s ease;
}
.card:hover .visual-area svg { transform: scale(1.1); }
.visual-area .layer-root { stroke: var(--text-sub); color: var(--text-sub); opacity: 0.7; stroke-width: 2; }
.visual-area .layer-prefix {
    stroke: color-mix(in srgb, var(--theme-color) 40%, transparent);
    color: color-mix(in srgb, var(--theme-color) 40%, transparent);
    stroke-width: 2.5;
    transition: opacity 0.3s ease, transform 0.3s ease;
}
.card.prefix-hidden .visual-area .layer-prefix { opacity: 0; transform: scale(0.8); }

.word-area {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 0.5rem;
}
.word-text {
    font-size: 2rem;
    font-weight: 800;
    color: var(--theme-color);
    min-width: 0;
    word-break: break-all;
}
.hint-text { font-size: 0.8rem; color: var(--text-sub); text-align: center; }


/* --- 组件: 单词卡片背面 --- */
.card-back {
    transform: rotateY(180deg);
    padding: 2rem 1.5rem;
    text-align: left;
    background-color: var(--card-back-bg);
    gap: 1.5rem;
    transition: justify-content 0.3s ease;
}
body.mode-immersive .card-back { justify-content: center; }

.breakdown-box {
    font-family: 'Courier New', monospace;
    background: var(--border-color);
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    text-align: center;
    font-weight: bold;
    color: var(--text-code);
    flex-shrink: 0;
    transition: opacity 0.3s ease-in-out; /* 为焦点模式淡出添加过渡 */
}
body.mode-immersive .breakdown-box { display: none; }

.meaning-section {
    flex-shrink: 0;
    transition: opacity 0.3s ease-in-out; /* 为焦点模式淡出添加过渡 */
}
.cn-translation { font-size: 1.4rem; color: var(--text-highlight); margin-bottom: 0.5rem; }
.imagery-text {
    font-size: 0.95rem;
    color: var(--text-sub);
    line-height: 1.4;
    font-style: italic;
    border-left: 3px solid var(--border-imagery);
    padding-left: 10px;
}

.sentence-section {
    position: relative; /* 为内部绝对定位的元素提供参照 */
    flex-grow: 1;
    overflow-y: auto;
    min-height: 0;
    background: var(--card-back-section-bg);
    padding: 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    -webkit-overflow-scrolling: touch;
    overscroll-behavior: contain;
    /* 为焦点模式的 expand-in 动画添加过渡 */
    transition: transform 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94), opacity 0.3s ease;
}
.sentence-block + .sentence-block {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}
.sentence-en { font-weight: 500; margin-bottom: 0.5rem; color: var(--text-main); }
.sentence-cn { font-size: 0.9rem; color: var(--text-sub); margin-bottom: 0.8rem; }


/* --- 【新增】例句焦点模式 --- */
/* 当卡片进入例句焦点模式时，模糊其他内容 */
.card.sentence-focus-active .breakdown-box,
.card.sentence-focus-active .meaning-section {
    opacity: 0.1;
    pointer-events: none; /* 防止交互 */
}

/* 焦点模式下的例句容器 */
.sentence-section.is-expanded {
    position: absolute;
    /* inset: 0 占满整个卡片背面，提供最大阅读空间 */
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 50; /* 确保在最顶层 */
    background-color: var(--card-back-bg); /* 使用卡片背面背景色，保持视觉一致 */
    border-radius: var(--radius-lg); /* 保持圆角 */
    padding: 2rem 1.5rem 1.5rem; /* 调整内边距以适应更大的空间 */
    border: none;
    animation: expand-in 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
}

/* 焦点模式的进入动画 */
@keyframes expand-in {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

/* 关闭焦点模式的按钮 */
.close-focus-btn {
    position: absolute;
    top: 0.8rem;
    right: 0.8rem;
    width: 32px;
    height: 32px;
    border: none;
    background: rgba(0,0,0,0.08);
    color: var(--text-sub);
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    z-index: 55; /* 在滚动内容之上 */
    display: flex; /* 使用 flex 居中叉号 */
    align-items: center;
    justify-content: center;
    opacity: 0; /* 默认不可见 */
    pointer-events: none; /* 默认不可交互 */
    transition: opacity 0.3s ease, background-color 0.2s ease, transform 0.2s ease;
}

.sentence-section.is-expanded .close-focus-btn {
    opacity: 1;
    pointer-events: auto;
}

.close-focus-btn:hover {
    background: rgba(0,0,0,0.15);
    color: var(--text-main);
    transform: scale(1.1);
}

body.dark-mode .close-focus-btn { background: rgba(255,255,255,0.1); }
body.dark-mode .close-focus-btn:hover { background: rgba(255,255,255,0.2); }

/* 【新增】滚动提示，告知用户此处可滚动 */
.scroll-hint {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 35px; /* 提示区域的高度 */
    background: linear-gradient(to top, var(--card-back-section-bg) 60%, transparent);
    pointer-events: none; /* 不干扰滚动 */
    border-bottom-left-radius: var(--radius-sm);
    border-bottom-right-radius: var(--radius-sm);
    display: flex;
    justify-content: center;
    align-items: flex-end;
    padding-bottom: 2px;
    opacity: 0.8;
}

.scroll-hint::after {
    content: '⌄';
    font-size: 1.5rem;
    color: var(--text-sub);
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-5px); }
    60% { transform: translateY(-3px); }
}


/* --- 组件: 按钮与图标 --- */
.toggle-prefix-btn, .mark-btn {
    position: absolute;
    width: 32px;
    height: 32px;
    background: none;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    color: var(--text-sub);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    z-index: 10;
}
.toggle-prefix-btn { top: 1rem; right: 1rem; }
.mark-btn { bottom: 1rem; right: 1rem; }
.toggle-prefix-btn:hover, .mark-btn:hover { background-color: rgba(0,0,0,0.05); }
body.dark-mode .toggle-prefix-btn:hover, body.dark-mode .mark-btn:hover { background-color: rgba(255,255,255,0.1); }
.mark-btn:hover { transform: scale(1.1); }
.toggle-prefix-btn svg, .mark-btn svg { width: 20px; height: 20px; }
.mark-btn svg { width: 24px; height: 24px; }
.toggle-prefix-btn .icon-eye { display: block; }
.toggle-prefix-btn .icon-eye-off { display: none; }
.card.prefix-hidden .toggle-prefix-btn .icon-eye { display: none; }
.card.prefix-hidden .toggle-prefix-btn .icon-eye-off { display: block; }
.mark-btn .icon-check-empty { display: block; }
.mark-btn .icon-check-filled { display: none; }
.card.is-learned .mark-btn .icon-check-empty { display: none; }
.card.is-learned .mark-btn .icon-check-filled { display: block; color: var(--theme-color); }

.audio-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: inherit;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 4px;
    border-radius: 50%;
    transition: background 0.2s;
}
.audio-btn:hover { background: rgba(0,0,0,0.05); }
body.dark-mode .audio-btn:hover { background: rgba(255,255,255,0.1); }
.word-audio { width: 32px; height: 32px; color: var(--text-sub); }

.note-btn { width: 32px; height: 32px; color: var(--text-sub); }
.note-btn svg { width: 20px; height: 20px; }
.note-btn .icon-note-empty { display: block; }
.note-btn .icon-note-filled { display: none; }
.note-btn.has-note .icon-note-empty { display: none; }
.note-btn.has-note .icon-note-filled { display: block; }
.note-btn.has-note { color: var(--theme-color); }

.sentence-audio {
    width: 100%;
    padding: 6px;
    border-radius: 4px;
    background: var(--bg-color);
    font-size: 0.85rem;
    font-weight: 600;
    justify-content: center;
}
.sentence-audio:hover { background: var(--border-color); }

/* --- 卡片笔记浮层 --- */
.card-note-overlay {
    position: absolute;
    inset: 0;
    background-color: var(--card-bg);
    z-index: 20;
    display: flex;
    flex-direction: column;
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    animation: fadeIn 0.2s ease-out;
}
.card-note-overlay.is-hidden { display: none; }
.note-input {
    flex-grow: 1;
    width: 100%;
    margin-bottom: 1rem;
    border: none;
    background-color: transparent;
    font-family: inherit;
    font-size: 1rem;
    line-height: 1.6;
    color: var(--text-main);
    resize: none;
    outline: none;
    background-image: linear-gradient(transparent 96%, var(--border-color) 96%);
    background-size: 100% 1.6rem;
    background-attachment: local;
}
.note-input::placeholder { color: var(--text-sub); font-style: italic; }
.note-actions { display: flex; justify-content: flex-end; gap: 0.5rem; }
.note-action-btn {
    padding: 6px 16px;
    border-radius: 4px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    border: 1px solid var(--border-color);
    background: var(--bg-secondary-color);
    color: var(--text-main);
    transition: all 0.2s ease;
}
.btn-save { background-color: var(--theme-color); color: var(--text-inverse); border-color: var(--theme-color); }

/* --- 组件: 前缀介绍卡片 --- */
.prefix-intro-card .card-front, .prefix-intro-card .card-back { background: var(--card-bg); }
body:not(.dark-mode) .prefix-intro-card .card-front,
body:not(.dark-mode) .prefix-intro-card .card-back { background: linear-gradient(135deg, #ffffff 0%, #f8fafc 100%); }
.prefix-intro-card .intro-title {
    font-size: 2.2rem;
    font-weight: 800;
    letter-spacing: 1px;
    font-family: 'Georgia', serif;
    color: var(--theme-color);
}
.prefix-intro-card .card-back { display: flex; flex-direction: column; justify-content: center; gap: 2rem; }
.prefix-intro-card .intro-section { padding: 0 1rem; }
.prefix-intro-card .intro-section-title {
    font-size: 1.1rem;
    color: var(--text-main);
    margin-bottom: 0.5rem;
    border-bottom: 2px solid;
    padding-bottom: 0.3rem;
    font-weight: 700;
    border-color: var(--theme-color);
}
.prefix-intro-card .intro-description, .prefix-intro-card .intro-imagery { font-size: 1rem; color: var(--text-sub); line-height: 1.6; }
.prefix-intro-card .intro-imagery { font-style: italic; }
.prefix-intro-card .visual-area svg { color: var(--theme-color); }

/* --- 组件: 骨架加载图 --- */
#skeleton-loader {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
    grid-column: 1 / -1;
    transition: opacity 0.3s ease-out;
}
.skeleton-card {
    height: 400px;
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 2rem 1.5rem;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    overflow: hidden;
    position: relative;
}
.skeleton-badge, .skeleton-visual, .skeleton-word, .skeleton-hint {
    background-color: var(--border-color);
    border-radius: 4px;
    animation: pulse 1.5s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
}
.skeleton-badge { position: absolute; top: 1rem; left: 1rem; width: 60px; height: 20px; border-radius: var(--radius-sm); }
.skeleton-visual { width: 120px; height: 120px; border-radius: 50%; margin: auto; }
.skeleton-word { width: 60%; height: 36px; margin: 0 auto 1rem; border-radius: var(--radius-sm); }
.skeleton-hint { width: 40%; height: 16px; margin: 0 auto; }


/* ==========================================================================
   移动端响应式适配 (Breakpoint: 768px)
   ========================================================================== */
@media screen and (max-width: 768px) {
    .card {
        height: 100%;
        min-width: 90vw;
        max-width: 95vw;
        scroll-snap-align: center;
        flex-shrink: 0;
        margin: 0;
    }

    .card.is-pending-removal {
        min-width: 0;
        margin-right: -1rem;
    }

    #skeleton-loader {
        display: flex;
        overflow-x: auto;
        gap: 1rem;
        height: 100%;
        min-height: auto;
        padding: 0;
        flex-grow: 1;
    }
    .skeleton-card {
        min-width: 90vw;
        height: 100%;
        margin: 0;
    }

    .card-front, .card-back { padding: 1.5rem 1rem; }
    .word-text { font-size: 1.8rem; }
    .visual-area svg { width: 100px; height: 100px; }
    .cn-translation { font-size: 1.3rem; }
    .sentence-en { font-size: 0.95rem; }

    /* 【新增】移动端焦点模式样式调整 */
    .sentence-section.is-expanded {
        padding: 1.5rem 1rem 1rem;
    }
    .close-focus-btn {
        top: 0.5rem;
        right: 0.5rem;
    }
}