/* ============================================
   My Aviation - Knowledge CSS
   航空知识版块样式 — 儿童友好版
   ============================================ */

/* ---------- 卡片网格 ---------- */
.knowledge-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-2xl);
}

.knowledge-card {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    border: 3px solid var(--color-cloud-2);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.knowledge-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: var(--color-sky-2);
}

.knowledge-card-link {
    display: block;
    text-decoration: none;
    color: var(--color-text-1);
}

.knowledge-card-image {
    position: relative;
    height: 170px;
    overflow: hidden;
}

.knowledge-card-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.knowledge-card-placeholder {
    position: relative;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    background: linear-gradient(135deg, var(--color-cloud), var(--color-cloud-2));
    color: var(--color-sky-2);
}

/* 分类专属背景色 */
.kcat-principle .knowledge-card-placeholder {
    background: linear-gradient(135deg, #5BB3FF 0%, #2B8FE0 100%);
}

.kcat-structure .knowledge-card-placeholder {
    background: linear-gradient(135deg, #63D37C 0%, #2F9E44 100%);
}

.kcat-history .knowledge-card-placeholder {
    background: linear-gradient(135deg, #FFC65C 0%, #F08C00 100%);
}

.kcat-fun .knowledge-card-placeholder {
    background: linear-gradient(135deg, #FF8A8A 0%, #FF6B6B 100%);
}

.kcat-units .knowledge-card-placeholder {
    background: linear-gradient(135deg, #B39DFB 0%, #7048E8 100%);
}

/* 装饰云朵 */
.kcard-cloud {
    position: absolute;
    background: rgba(255, 255, 255, 0.22);
    border-radius: 50%;
}

.kcard-cloud-1 {
    width: 96px;
    height: 96px;
    top: -30px;
    right: -20px;
}

.kcard-cloud-2 {
    width: 44px;
    height: 44px;
    left: 18px;
    bottom: 16px;
    background: rgba(255, 255, 255, 0.16);
}

/* 分类大图标：半嵌卡片、带弹跳动效 */
.kcard-icon {
    font-size: 3.3rem;
    color: rgba(255, 255, 255, 0.95);
    filter: drop-shadow(0 4px 12px rgba(27, 111, 191, 0.25));
    transform: translateY(6px) rotate(-4deg);
    transition: transform var(--transition-base);
}

.knowledge-card:hover .kcard-icon {
    transform: translateY(0) rotate(4deg) scale(1.1);
}

.knowledge-card-badge {
    position: absolute;
    top: 0.75rem;
    left: 0.75rem;
    background: var(--color-white);
    color: var(--color-sky-deep);
    font-size: 0.8rem;
    font-weight: 800;
    padding: 0.32rem 0.85rem;
    border-radius: var(--radius-full);
    box-shadow: var(--shadow-sm);
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
}

.knowledge-card-badge i {
    font-size: 0.75rem;
}

.knowledge-card-body {
    padding: var(--spacing-md);
}

.knowledge-card-title {
    font-size: 1.1rem;
    font-weight: 800;
    color: var(--color-sky-deep);
    margin-bottom: var(--spacing-xs);
    line-height: 1.4;
    min-height: 3rem;
}

.knowledge-card-excerpt {
    color: var(--color-text-2);
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
    min-height: 3rem;
}

.knowledge-card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-top: 2px solid var(--color-cloud-2);
    padding-top: var(--spacing-sm);
}

.knowledge-card-date {
    color: var(--color-text-3);
    font-size: 0.82rem;
}

.knowledge-card-cta {
    color: var(--color-sky-1);
    font-weight: 700;
    font-size: 0.92rem;
}

/* ---------- 归档页头部 ---------- */
.knowledge-archive-header {
    text-align: center;
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

.knowledge-archive-header .archive-title {
    font-size: 2.2rem;
    color: var(--color-sky-deep);
    margin-bottom: var(--spacing-sm);
}

.knowledge-archive-header .archive-description {
    color: var(--color-text-2);
    font-size: 1.05rem;
    max-width: 640px;
    margin: 0 auto;
}

/* ---------- 分类筛选标签 ---------- */
.knowledge-filter-tabs {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.knowledge-filter-tab {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.55rem 1.2rem;
    border-radius: var(--radius-full);
    background: var(--color-cloud);
    color: var(--color-text-1);
    font-weight: 700;
    text-decoration: none;
    border: 3px solid var(--color-cloud-2);
    transition: all var(--transition-fast);
}

.knowledge-filter-tab:hover {
    background: var(--color-cloud-2);
    color: var(--color-sky-1);
    border-color: var(--color-sky-2);
    transform: translateY(-2px);
}

.knowledge-filter-tab.active {
    background: var(--color-sky-1);
    border-color: var(--color-sky-1);
    color: var(--color-white);
    box-shadow: var(--shadow-sun);
}

.knowledge-result-count {
    text-align: center;
    color: var(--color-text-3);
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
}

.knowledge-empty {
    text-align: center;
    padding: var(--spacing-2xl) 0;
    color: var(--color-text-3);
}

.knowledge-empty i {
    font-size: 3rem;
    display: block;
    margin-bottom: var(--spacing-md);
    color: var(--color-sky-2);
}

/* ---------- 详情页 ---------- */
.knowledge-detail-hero {
    background: linear-gradient(160deg, var(--color-sky-1), var(--color-sky-2));
    padding: var(--spacing-3xl) 0 var(--spacing-2xl);
    position: relative;
    overflow: hidden;
}

.knowledge-detail-hero-bg {
    position: absolute;
    inset: 0;
    background:
        radial-gradient(circle at 12% 20%, rgba(255,255,255,0.18) 0, rgba(255,255,255,0.18) 60px, transparent 61px),
        radial-gradient(circle at 88% 75%, rgba(255,255,255,0.14) 0, rgba(255,255,255,0.14) 90px, transparent 91px),
        radial-gradient(circle at 70% 15%, rgba(255,255,255,0.1) 0, rgba(255,255,255,0.1) 40px, transparent 41px);
}

.knowledge-detail-header {
    position: relative;
    text-align: center;
    color: var(--color-white);
}

.knowledge-category-tag {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    background: rgba(255,255,255,0.22);
    color: var(--color-white);
    font-weight: 700;
    padding: 0.4rem 1.1rem;
    border-radius: var(--radius-full);
    text-decoration: none;
    margin-bottom: var(--spacing-md);
}

.knowledge-category-tag:hover {
    background: rgba(255,255,255,0.32);
    color: var(--color-white);
}

.knowledge-detail-title {
    font-size: 2.4rem;
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    line-height: 1.3;
}

.knowledge-detail-meta {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    font-size: 0.95rem;
    opacity: 0.95;
}

.knowledge-detail-meta span {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

.knowledge-detail-body {
    max-width: 780px;
    margin: 0 auto;
    padding: var(--spacing-2xl) 0;
}

.knowledge-detail-cover {
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: var(--spacing-xl);
    box-shadow: var(--shadow-md);
}

.knowledge-detail-cover img {
    width: 100%;
    height: auto;
    display: block;
}

.knowledge-detail-content {
    font-size: 1.05rem;
    line-height: 1.9;
    color: var(--color-text-1);
}

.knowledge-detail-content h1,
.knowledge-detail-content h2,
.knowledge-detail-content h3 {
    color: var(--color-sky-deep);
    margin: var(--spacing-lg) 0 var(--spacing-sm);
}

.knowledge-detail-content p {
    margin-bottom: var(--spacing-md);
}

.knowledge-detail-content ul,
.knowledge-detail-content ol {
    margin: var(--spacing-sm) 0 var(--spacing-lg) var(--spacing-lg);
}

.knowledge-detail-content li {
    margin-bottom: 0.6rem;
}

.knowledge-detail-content img {
    max-width: 100%;
    border-radius: var(--radius-md);
}

.knowledge-detail-back {
    margin-top: var(--spacing-2xl);
    text-align: center;
}

/* ---------- 相关推荐 ---------- */
.related-knowledge-section {
    background: var(--color-cloud);
    padding: var(--spacing-3xl) 0;
    border-top: 3px solid var(--color-cloud-2);
}

/* ---------- 首页航空小课堂 ---------- */
.knowledge-classroom-section {
    background: linear-gradient(180deg, var(--color-cloud), var(--color-white));
}