/* ==========================================================================
   PinPin Visual Identity (PPVI) 核心体系
   ========================================================================== */

:root {
  /* 1. 灰阶为基 (Color is punctuation, not prose) */
  --bg-base: #e8e8e8;
  --bg-gradient: linear-gradient(145deg, #f5f5f5 0%, #e0e0e0 100%);
  --color-ink: #1a1a1a;
  --color-ink-muted: #5c5c5c;
  --color-ink-faint: #8a8a8a;

  /* 点缀色 (≤15%) - 仅用于交互反馈、图标点缀和标签 */
  --color-accent: #ea580c;
  --color-accent-soft: rgba(234, 88, 12, 0.08);

  /* 2. 严格层级 (Every size has a reason) - 5级 Fluid Typography */
  --text-display: clamp(48px, 6vw, 86px);
  --text-headline: clamp(32px, 4vw, 48px);
  --text-subtitle: clamp(20px, 2.5vw, 24px);
  --text-body: clamp(16px, 1.5vw, 18px);
  --text-caption: clamp(13px, 1vw, 14px);

  --weight-read: 400;
  --weight-loud: 550;
  --weight-declare: 700;

  /* 字体栈 */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "SF Mono", "Cascadia Code", "JetBrains Mono", Consolas, monospace;

  /* 3. 玻璃拟态 (Depth through light) */
  --glass-bg: rgba(255, 255, 255, 0.55);
  --glass-border: rgba(255, 255, 255, 0.4);
  --glass-shadow: 0 12px 32px -12px rgba(0, 0, 0, 0.08);

  /* 4. 密度呼吸 */
  --spacing-card-pad: 24px;
  --spacing-grid-gap: 32px;
  --radius-card: 16px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  color: var(--color-ink);
  background: var(--bg-gradient);
  background-attachment: fixed;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  /* 中文排版优化三件套 */
  word-break: keep-all;
  overflow-wrap: anywhere;
}

::selection { background: var(--color-accent-soft); color: var(--color-accent); }

/* 噪点纹理层 (玻璃拟态质感增强) */
.noise-overlay {
  position: fixed; inset: 0; z-index: -1; pointer-events: none; opacity: 0.04;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noiseFilter'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.8' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noiseFilter)'/%3E%3C/svg%3E");
}

.container { max-width: 1280px; margin: 0 auto; padding: 0 clamp(24px, 4vw, 48px); }

/* ── Hero 区块 ── */
.hero { padding: 96px 0 64px; }
.display-title { font-size: var(--text-display); font-weight: var(--weight-declare); letter-spacing: -0.02em; line-height: 1.1; margin-bottom: 24px; text-wrap: balance; }
.display-title span { color: var(--color-accent); font-family: var(--font-mono); }
.hero-lead { font-size: var(--text-subtitle); color: var(--color-ink-muted); max-width: 65ch; line-height: 1.5; font-weight: var(--weight-read); text-wrap: balance; }

/* ── 交互控制区 (视觉上浮) ── */
.controls-wrapper {
  position: sticky; top: 0; z-index: 100;
  padding: 24px 0 16px;
  /* 背景虚化融合 */
  background: linear-gradient(180deg, rgba(224,224,224,0.9) 0%, rgba(224,224,224,0) 100%);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  margin-bottom: 32px;
}

.search-bar {
  position: relative; margin-bottom: 20px;
  max-width: 600px;
}
.search-bar input {
  width: 100%;
  font-family: var(--font-sans); font-size: var(--text-body);
  padding: 16px 20px 16px 52px;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: 12px; color: var(--color-ink);
  backdrop-filter: blur(32px); -webkit-backdrop-filter: blur(32px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.03);
  outline: none; transition: all 0.2s ease;
}
.search-bar input:focus {
  border-color: var(--color-accent);
  background: rgba(255,255,255,0.8);
  box-shadow: 0 0 0 4px var(--color-accent-soft);
}
.search-bar svg { position: absolute; left: 20px; top: 50%; transform: translateY(-50%); width: 20px; height: 20px; color: var(--color-ink-faint); }

.filter-chips { display: flex; flex-wrap: wrap; gap: 10px; }
.chip {
  font-size: var(--text-caption); font-weight: var(--weight-loud);
  padding: 8px 16px; border-radius: 999px; cursor: pointer;
  background: var(--glass-bg); border: 1px solid var(--glass-border);
  color: var(--color-ink-muted);
  backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  transition: all 0.2s ease; display: inline-flex; align-items: center; gap: 6px;
}
.chip:hover { border-color: rgba(0,0,0,0.1); color: var(--color-ink); }
.chip.active { background: var(--color-ink); color: #fff; border-color: var(--color-ink); }
.chip-count { font-family: var(--font-mono); font-size: 11px; opacity: 0.6; }

/* ── 内容区域 ── */
.section-category { padding-top: 48px; border-top: 1px solid rgba(0,0,0,0.04); margin-top: 48px; scroll-margin-top: 140px; }
.category-header { display: flex; align-items: baseline; gap: 16px; margin-bottom: 24px; }
.category-title { font-size: var(--text-headline); font-weight: var(--weight-declare); letter-spacing: -0.01em; }
.category-count { font-family: var(--font-mono); font-size: var(--text-caption); color: var(--color-ink-faint); }
.category-desc { font-size: var(--text-body); color: var(--color-ink-muted); margin-bottom: 32px; max-width: 600px; }

/* 网格系统 (自适应呼吸) */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--spacing-grid-gap);
}

/* 玻璃拟态卡片 */
.command-card, .common-card {
  background: var(--glass-bg);
  backdrop-filter: blur(48px); -webkit-backdrop-filter: blur(48px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-card);
  padding: var(--spacing-card-pad);
  min-width: 0; /* 阻止内容撑爆网格 */
  box-shadow: var(--glass-shadow);
  display: flex; flex-direction: column;
  transition: transform 0.2s cubic-bezier(0.1, 0, 0.2, 1), box-shadow 0.2s ease;
  text-decoration: none;
  color: inherit;
}
.command-card:hover, .common-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 20px 48px -12px rgba(0, 0, 0, 0.1);
  background: rgba(255,255,255,0.7);
}

.card-head { display: flex; align-items: baseline; flex-wrap: wrap; gap: 8px 12px; margin-bottom: 12px; }
.cmd-name { font-family: var(--font-mono); font-size: var(--text-subtitle); font-weight: var(--weight-declare); color: var(--color-ink); letter-spacing: -0.02em; }
.cmd-alias { font-family: var(--font-mono); font-size: var(--text-caption); color: var(--color-ink-faint); background: rgba(0,0,0,0.04); padding: 2px 8px; border-radius: 4px; }

.cmd-tagline { font-size: var(--text-body); font-weight: var(--weight-loud); color: var(--color-accent); margin-bottom: 16px; display: flex; align-items: center; gap: 8px; }
.cmd-tagline::before { content: ""; display: block; width: 4px; height: 16px; background: var(--color-accent); border-radius: 2px; }

.cmd-explain { font-size: var(--text-body); color: var(--color-ink-muted); margin-bottom: 24px; flex: 1; }

.card-footer { border-top: 1px solid rgba(0,0,0,0.06); padding-top: 16px; display: flex; flex-direction: column; gap: 8px; }
.meta-row { display: flex; align-items: flex-start; gap: 12px; font-size: var(--text-caption); color: var(--color-ink-faint); }
.meta-label { font-weight: var(--weight-loud); color: var(--color-ink); flex-shrink: 0; min-width: 48px; }

mark { background: var(--color-accent-soft); color: var(--color-accent); border-radius: 3px; padding: 0 4px; font-weight: var(--weight-loud); }
.empty-state { text-align: center; padding: 120px 0; font-size: var(--text-subtitle); color: var(--color-ink-faint); display: none; }

/* ── 页脚 Footer ── */
footer {
  border-top: 1px solid rgba(0, 0, 0, 0.06);
  margin-top: 64px;
  padding: 48px 0 64px;
  font-size: var(--text-caption);
  color: var(--color-ink-faint);
}
.footer-content { display: flex; flex-wrap: wrap; gap: 24px; justify-content: space-between; align-items: flex-end; }
.footer-source { max-width: 600px; line-height: 1.7; }
.footer-source a { color: var(--color-ink-muted); text-decoration: none; border-bottom: 1px solid rgba(0,0,0,0.1); transition: color 0.2s; }
.footer-source a:hover { color: var(--color-ink); border-bottom-color: var(--color-ink); }
.footer-ppvi { font-family: var(--font-mono); font-size: 11px; text-align: right; }
.footer-copyright {
  margin-top: 32px; padding-top: 24px;
  text-align: center; font-family: var(--font-mono);
  font-size: 12px; letter-spacing: 0.02em;
}

@media (max-width: 768px) {
  .hero { padding: 64px 0 32px; }
}

/* 导航栏 */
.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 48px;
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(232, 232, 232, 0.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(0,0,0,0.05);
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--color-ink);
  font-weight: var(--weight-declare);
  font-size: var(--text-subtitle);
}
.brand img {
  height: 32px;
  width: auto;
}
.nav-links a {
  text-decoration: none;
  color: var(--color-ink-muted);
  font-weight: var(--weight-loud);
  font-size: var(--text-body);
  transition: color 0.2s;
}
.nav-links a:hover {
  color: var(--color-ink);
}

@media (max-width: 768px) {
  .site-header { padding: 16px 24px; }
}

/* 书籍与课程图片占位 */
.image-placeholder {
  width: 100%;
  aspect-ratio: 3/4;
  background: linear-gradient(135deg, #e0e0e0 0%, #cfcfcf 100%);
  border-radius: 8px;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-ink-faint);
  font-size: var(--text-caption);
  text-align: center;
  padding: 16px;
  overflow: hidden;
}
.image-placeholder img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 8px;
  display: block;
}
.course-card .image-placeholder {
  aspect-ratio: 16/9;
}

/* FAQ 折叠面板 */
details.faq {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  margin-bottom: 16px;
  box-shadow: var(--glass-shadow);
  overflow: hidden;
}
details.faq summary {
  padding: 20px 24px;
  font-size: var(--text-body);
  font-weight: var(--weight-loud);
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
details.faq summary::-webkit-details-marker { display: none; }
details.faq summary::after {
  content: '+';
  font-size: 20px;
  color: var(--color-accent);
  transition: transform 0.2s ease;
}
details.faq[open] summary::after {
  transform: rotate(45deg);
}
details.faq p {
  padding: 0 24px 24px;
  color: var(--color-ink-muted);
}