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

:root {
    --bg-primary: #0d0d0d;
    --bg-secondary: #161616;
    --bg-card: #1a1a1a;
    --bg-card-hover: #202020;
    --accent: #c084fc;
    --accent-dim: #a855f7;
    --text-primary: #f0f0f0;
    --text-secondary: #a0a0a0;
    --text-muted: #666;
    --border: #2a2a2a;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-primary);
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ── Header ── */
header {
    padding: 80px 20px 60px;
    text-align: center;
    position: relative;
    border-bottom: 1px solid var(--border);
}

header::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: radial-gradient(ellipse 80% 60% at 50% -10%, rgba(168, 85, 247, 0.18), transparent);
    pointer-events: none;
}

.header-label {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.2em;
    text-transform: uppercase;
    color: var(--accent);
    border: 1px solid rgba(168, 85, 247, 0.4);
    padding: 4px 14px;
    border-radius: 20px;
    margin-bottom: 20px;
}

header h1 {
    font-size: 2.8rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
    margin-bottom: 12px;
}

.subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    letter-spacing: 0.05em;
}

.subtitle span {
    color: var(--text-muted);
    margin: 0 8px;
}

/* ── Main ── */
main {
    padding: 60px 0;
}

.category {
    margin-bottom: 70px;
}

.category-header {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 32px;
}

.category-header h2 {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: 0.02em;
}

.category-line {
    flex: 1;
    height: 1px;
    background: linear-gradient(to right, var(--border), transparent);
}

.category-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--accent);
    flex-shrink: 0;
}

/* ── Video Card ── */
.video-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 28px;
    margin-bottom: 24px;
    transition: background 0.2s, border-color 0.2s;
}

.video-card:hover {
    background: var(--bg-card-hover);
    border-color: rgba(168, 85, 247, 0.3);
}

.video-card h3 {
    font-size: 1.15rem;
    color: var(--text-primary);
    margin-bottom: 18px;
    font-weight: 600;
}

.video-wrapper {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
    border-radius: 8px;
    background: #0a0a0a;
    margin-bottom: 16px;
}

.video-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.video-cover {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: #111 center/cover no-repeat;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}

.play-btn {
    background: rgba(168, 85, 247, 0.85);
    border: none;
    border-radius: 50%;
    width: 72px;
    height: 72px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background 0.2s, transform 0.2s;
}

.play-btn:hover {
    background: rgba(168, 85, 247, 1);
    transform: scale(1.1);
}

.description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.8;
    padding-left: 14px;
    border-left: 2px solid rgba(168, 85, 247, 0.5);
}

/* ── Summary ── */
.summary {
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 32px;
    background: var(--bg-secondary);
    position: relative;
    overflow: hidden;
}

.summary::before {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 3px;
    height: 100%;
    background: linear-gradient(to bottom, var(--accent), transparent);
}

.summary p {
    font-size: 0.95rem;
    color: var(--text-secondary);
    line-height: 1.9;
    margin-bottom: 12px;
}

.summary p:last-child {
    margin-bottom: 0;
    color: var(--text-muted);
    font-size: 0.875rem;
    font-style: italic;
}

/* ── Footer ── */
footer {
    border-top: 1px solid var(--border);
    padding: 28px 20px;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.85rem;
}

/* ── Responsive ── */
@media (max-width: 768px) {
    header h1 { font-size: 2rem; }

    .video-card { padding: 18px; }

    .video-card h3 { font-size: 1rem; }

    main { padding: 40px 0; }
}