/* ===== 知识点卡片 ===== */
.knowledge-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-light);
    overflow: hidden;
    margin-bottom: 10px;
    box-shadow: var(--shadow-sm);
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
}

.knowledge-card::after {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--border-light);
    transition: all 0.3s ease;
}

.knowledge-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-border);
    transform: translateX(2px);
}

.knowledge-card:hover::after {
    background: var(--primary-light);
    width: 4px;
}

.knowledge-card.learned::after {
    background: #16a34a;
}

.knowledge-card.learned:hover::after {
    background: #22c55e;
}

.knowledge-link {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 20px;
    text-decoration: none;
    color: var(--text-secondary);
    transition: background 0.15s;
}

.knowledge-link:hover {
    background: #fafbfd;
}

.knowledge-icon {
    width: 40px;
    height: 40px;
    border-radius: 11px;
    background: var(--primary-bg);
    color: var(--primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    flex-shrink: 0;
    font-weight: 700;
    transition: transform 0.25s ease;
}

.knowledge-card:hover .knowledge-icon {
    transform: scale(1.1);
}

.knowledge-card.learned .knowledge-icon {
    background: #f0fdf4;
    color: #16a34a;
}

.knowledge-info {
    flex: 1;
    min-width: 0;
}

.knowledge-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 3px;
    line-height: 1.4;
}

.knowledge-meta {
    font-size: 0.76rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 8px;
}

.knowledge-status-badge {
    display: inline-flex;
    align-items: center;
    gap: 3px;
    font-size: 0.7rem;
    padding: 2px 8px;
    border-radius: 8px;
    font-weight: 600;
}

.knowledge-status-badge.done {
    background: #dcfce7;
    color: #15803d;
}

.knowledge-status-badge.pending {
    background: #f8fafc;
    color: #94a3b8;
    border: 1px solid #e2e8f0;
}

.knowledge-arrow {
    color: var(--text-muted);
    font-size: 0.95rem;
    flex-shrink: 0;
    transition: all 0.25s ease;
}

.knowledge-link:hover .knowledge-arrow {
    color: var(--primary);
    transform: translateX(4px);
}

/* ===== 返回按钮 ===== */
.back-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    width: 100%;
    margin-top: 16px;
    padding: 12px;
    border: 1.5px solid var(--border);
    border-radius: 12px;
    background: var(--surface);
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: var(--font);
    box-shadow: var(--shadow-sm);
}

.back-btn:hover {
    border-color: var(--primary-light);
    color: var(--primary);
    background: var(--primary-bg);
    box-shadow: var(--shadow);
    transform: translateY(-1px);
}

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

/* ===== 空状态 ===== */
.empty-state-page {
    text-align: center;
    padding: 64px 20px;
    color: var(--text-muted);
}

.empty-state-page .empty-icon {
    font-size: 3.2rem;
    margin-bottom: 14px;
    display: block;
}

.empty-state-page h3 {
    margin: 0 0 6px 0;
    color: var(--text);
    font-size: 1.05rem;
}

.empty-state-page p {
    font-size: 0.88rem;
    color: var(--text-muted);
}

/* ===== 计数标签 ===== */
.count-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 14px;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 6px;
}

.count-label strong {
    color: var(--primary);
    font-weight: 700;
}

/* ===== 响应式 ===== */
@media (max-width: 640px) {
    .knowledge-card:hover { transform: none; }
    .knowledge-link { padding: 12px 16px; gap: 12px; }
    .knowledge-icon { width: 36px; height: 36px; border-radius: 10px; font-size: 1rem; }
    .knowledge-title { font-size: 0.85rem; }
    .back-btn { margin-top: 12px; padding: 11px; }
}