/* ==========================================================================
   Video2Frame 全站公共样式表
   遵循 2026 百度搜索优质内容白皮书：移动优先、Core Web Vitals 优化、CLS 趋近零
   ========================================================================== */

/* ---------- 全局重置 & 设计变量 ---------- */
:root {
  --primary: #2563eb;
  --primary-light: #3b82f6;
  --primary-dark: #1d4ed8;
  --primary-bg: #eff6ff;
  --gray-50: #f8fafc;
  --gray-100: #f1f5f9;
  --gray-200: #e2e8f0;
  --gray-300: #cbd5e1;
  --gray-400: #94a3b8;
  --gray-500: #64748b;
  --gray-600: #475569;
  --gray-700: #334155;
  --gray-800: #1e293b;
  --gray-900: #0f172a;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --transition-base: all 0.24s ease;
  --header-h: 64px;
}

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

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: linear-gradient(135deg, #f8fafc 0%, #f0f7ff 100%);
  min-height: 100vh;
  color: var(--gray-700);
  line-height: 1.7;
  padding-top: var(--header-h);
}

img { max-width: 100%; height: auto; display: block; }
a { color: var(--primary); text-decoration: none; transition: var(--transition-base); }
a:hover { color: var(--primary-dark); text-decoration: underline; }

.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

/* ---------- 顶部导航 ---------- */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  height: var(--header-h);
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--gray-200);
  display: flex; align-items: center;
}
.nav-wrap { width: 100%; max-width: 1200px; margin: 0 auto; padding: 0 20px; display: flex; align-items: center; justify-content: space-between; }
.nav-logo { font-size: 20px; font-weight: 800; color: var(--gray-900); display: flex; align-items: center; gap: 8px; text-decoration: none; }
.nav-logo:hover { text-decoration: none; }
.nav-logo .logo-icon { width: 32px; height: 32px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); border-radius: 8px; display: flex; align-items: center; justify-content: center; color: #fff; font-size: 18px; }
.nav-menu { display: flex; align-items: center; gap: 4px; list-style: none; }
.nav-menu a { color: var(--gray-700); font-size: 15px; font-weight: 500; padding: 8px 14px; border-radius: var(--radius-sm); }
.nav-menu a:hover, .nav-menu a.active { color: var(--primary); background: var(--primary-bg); text-decoration: none; }
.nav-toggle { display: none; background: none; border: none; cursor: pointer; padding: 8px; }
.nav-toggle span { display: block; width: 24px; height: 2px; background: var(--gray-700); border-radius: 2px; transition: var(--transition-base); }
.nav-toggle span + span { margin-top: 5px; }
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- 面包屑 ---------- */
.breadcrumb { padding: 16px 0; font-size: 13px; color: var(--gray-500); }
.breadcrumb ol { list-style: none; display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.breadcrumb li { display: flex; align-items: center; gap: 6px; }
.breadcrumb li::after { content: "/"; color: var(--gray-300); margin-left: 6px; }
.breadcrumb li:last-child::after { content: ""; }
.breadcrumb a { color: var(--gray-500); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb li:last-child { color: var(--gray-700); font-weight: 500; }

/* ---------- 通用标题 ---------- */
h1, h2, h3, h4 { color: var(--gray-900); line-height: 1.35; }
h1 { font-size: 32px; font-weight: 800; margin-bottom: 12px; }
h2 { font-size: 26px; font-weight: 700; margin-bottom: 16px; }
h3 { font-size: 20px; font-weight: 600; margin-bottom: 12px; }
h4 { font-size: 16px; font-weight: 600; margin-bottom: 8px; }
p { margin-bottom: 14px; }

.section { padding: 48px 0; }
.section-tight { padding: 32px 0; }
.section-title { text-align: center; margin-bottom: 36px; }
.section-title h2 { margin-bottom: 10px; }
.section-title .sub { color: var(--gray-500); font-size: 15px; max-width: 680px; margin: 0 auto; }

/* ---------- Hero 区 ---------- */
.hero { padding: 56px 0 40px; text-align: center; }
.hero h1 { font-size: 36px; margin-bottom: 14px; }
.hero .lead { font-size: 17px; color: var(--gray-600); max-width: 760px; margin: 0 auto 20px; }
.tag-row { display: flex; gap: 10px; justify-content: center; margin-top: 18px; flex-wrap: wrap; }
.tag { padding: 5px 14px; background: var(--primary-bg); color: var(--primary); font-size: 13px; border-radius: 999px; font-weight: 500; }

/* ---------- 卡片 ---------- */
.card {
  background: #fff; border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md); padding: 28px; margin-bottom: 28px;
  transition: var(--transition-base);
}
.card:hover { box-shadow: var(--shadow-lg); }
.card-title { font-size: 20px; font-weight: 600; color: var(--gray-900); margin-bottom: 20px; display: flex; align-items: center; gap: 10px; }

/* ---------- 功能网格 ---------- */
.feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 20px; }
.feature-item { background: #fff; padding: 24px; border-radius: var(--radius-md); box-shadow: var(--shadow-sm); transition: var(--transition-base); border-top: 3px solid var(--primary); }
.feature-item:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.feature-item .ico { font-size: 28px; margin-bottom: 12px; }
.feature-item h3 { font-size: 17px; margin-bottom: 8px; }
.feature-item p { font-size: 14px; color: var(--gray-500); margin-bottom: 0; }

/* ---------- 上传区域 ---------- */
.upload-box {
  width: 100%; height: 240px;
  border: 2px dashed var(--gray-300); border-radius: var(--radius-md);
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  color: var(--gray-500); cursor: pointer; background: var(--gray-50);
  transition: var(--transition-base); position: relative;
}
.upload-box:hover { border-color: var(--primary-light); background: var(--primary-bg); }
.upload-box.drag-over { border-color: var(--primary); background: rgba(59,130,246,0.08); }
.upload-box svg { width: 52px; height: 52px; margin-bottom: 14px; fill: var(--gray-500); transition: var(--transition-base); }
.upload-box.drag-over svg, .upload-box:hover svg { fill: var(--primary); }
.upload-text-main { font-size: 16px; font-weight: 500; color: var(--gray-700); }
.upload-text-sub { font-size: 13px; margin-top: 6px; color: var(--gray-500); }

/* ---------- 表单 ---------- */
.row { display: flex; align-items: center; gap: 20px; margin-bottom: 24px; flex-wrap: wrap; }
.row-item { display: flex; align-items: center; gap: 8px; white-space: nowrap; }
.range-wrap { flex: 1; min-width: 360px; display: flex; flex-direction: column; gap: 8px; }
.range-top { display: flex; justify-content: space-between; font-size: 14px; color: var(--gray-700); }
input[type="range"] { width: 100%; height: 6px; background: var(--gray-200); border-radius: 99px; outline: none; -webkit-appearance: none; }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 18px; height: 18px; border-radius: 50%; background: var(--primary); cursor: pointer; border: 2px solid #fff; box-shadow: var(--shadow-sm); }
.time-group { display: flex; gap: 16px; flex-wrap: wrap; }
.time-input-item { display: flex; flex-direction: column; gap: 6px; }
label { font-size: 14px; color: var(--gray-700); font-weight: 500; }
input[type="number"], input[type="text"] { border: 1px solid var(--gray-300); padding: 10px 12px; border-radius: var(--radius-sm); font-size: 14px; color: var(--gray-900); transition: var(--transition-base); }
input[type="number"]:focus, input[type="text"]:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px rgba(37,99,235,0.12); }
.time-group input { width: 220px; }
.full-input { width: 100%; }

/* ---------- 按钮 ---------- */
button { padding: 11px 30px; border-radius: var(--radius-sm); cursor: pointer; font-size: 15px; font-weight: 500; border: none; transition: var(--transition-base); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--primary-light); box-shadow: 0 4px 12px rgba(37,99,235,0.25); }
.btn-success { background: var(--success); color: #fff; }
.btn-success:hover:not(:disabled) { filter: brightness(1.08); box-shadow: 0 4px 12px rgba(16,185,129,0.25); }
.btn-gray { background: var(--gray-500); color: #fff; padding: 7px 16px; font-size: 14px; }
.btn-gray:hover { background: var(--gray-700); }
.btn-outline { background: #fff; color: var(--primary); border: 1px solid var(--primary); padding: 10px 24px; }
.btn-outline:hover { background: var(--primary-bg); }
button:disabled { opacity: 0.55; cursor: not-allowed; box-shadow: none !important; }
.btn-group { display: flex; gap: 14px; margin-bottom: 10px; flex-wrap: wrap; }

/* ---------- 进度区 ---------- */
.progress-wrap { background: var(--gray-50); border: 1px solid var(--gray-200); border-radius: var(--radius-md); padding: 24px; min-height: 120px; }
.empty-tip { color: var(--gray-500); padding: 40px 0; text-align: center; font-size: 14px; }
.progress-bg { width: 100%; height: 26px; background: var(--gray-200); border-radius: 99px; overflow: hidden; margin-bottom: 12px; }
.progress-fill { height: 100%; width: 0%; background: linear-gradient(90deg, var(--primary), var(--primary-light)); transition: width 0.08s linear; border-radius: 99px; }
.progress-text { font-size: 14px; color: var(--gray-700); text-align: center; font-weight: 500; }

/* ---------- 日志框 ---------- */
textarea { width: 100%; min-height: 120px; margin-top: 8px; border: 1px solid var(--gray-300); padding: 12px; font-family: 'Consolas', monospace; font-size: 13px; border-radius: var(--radius-sm); background: #0f172a; color: #a5f3fc; resize: vertical; }

/* ---------- 文章正文 ---------- */
.article-body { font-size: 16px; color: var(--gray-700); }
.article-body h2 { margin-top: 36px; margin-bottom: 14px; padding-bottom: 8px; border-bottom: 2px solid var(--gray-200); }
.article-body h3 { margin-top: 24px; }
.article-body p { margin-bottom: 16px; }
.article-body ul, .article-body ol { margin: 0 0 16px 22px; }
.article-body li { margin-bottom: 8px; }
.article-body strong { color: var(--gray-900); }
.article-body blockquote { border-left: 4px solid var(--primary); background: var(--primary-bg); padding: 14px 18px; margin: 16px 0; border-radius: 0 var(--radius-sm) var(--radius-sm) 0; color: var(--gray-700); }
.article-body code { background: var(--gray-100); padding: 2px 6px; border-radius: 4px; font-size: 14px; color: var(--danger); }
.article-body table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 14px; }
.article-body th, .article-body td { border: 1px solid var(--gray-200); padding: 10px 14px; text-align: left; }
.article-body th { background: var(--gray-50); font-weight: 600; color: var(--gray-900); }
.article-body tr:nth-child(even) td { background: var(--gray-50); }

/* ---------- FAQ 手风琴 ---------- */
.faq-list { display: flex; flex-direction: column; gap: 12px; }
.faq-item { background: #fff; border: 1px solid var(--gray-200); border-radius: var(--radius-md); overflow: hidden; transition: var(--transition-base); }
.faq-item summary { padding: 18px 22px; font-size: 16px; font-weight: 600; color: var(--gray-900); cursor: pointer; list-style: none; display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after { content: "+"; font-size: 22px; color: var(--primary); font-weight: 300; transition: var(--transition-base); }
.faq-item[open] summary::after { transform: rotate(45deg); }
.faq-item[open] summary { border-bottom: 1px solid var(--gray-200); }
.faq-answer { padding: 16px 22px; font-size: 15px; color: var(--gray-600); }

/* ---------- 步骤 ---------- */
.steps { display: flex; flex-direction: column; gap: 24px; counter-reset: step; }
.step { display: flex; gap: 20px; align-items: flex-start; }
.step-num { flex-shrink: 0; width: 44px; height: 44px; border-radius: 50%; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: #fff; font-size: 18px; font-weight: 700; display: flex; align-items: center; justify-content: center; }
.step-body { flex: 1; }
.step-body h3 { margin-bottom: 6px; }

/* ---------- 对比表 ---------- */
.compare-table { width: 100%; border-collapse: collapse; font-size: 15px; background: #fff; border-radius: var(--radius-md); overflow: hidden; box-shadow: var(--shadow-sm); }
.compare-table th, .compare-table td { padding: 14px 18px; text-align: left; border-bottom: 1px solid var(--gray-200); }
.compare-table th { background: var(--gray-900); color: #fff; font-weight: 600; }
.compare-table tr:last-child td { border-bottom: none; }
.compare-table .yes { color: var(--success); font-weight: 600; }
.compare-table .no { color: var(--danger); font-weight: 600; }

/* ---------- CTA ---------- */
.cta-box { background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: #fff; border-radius: var(--radius-lg); padding: 40px; text-align: center; margin: 40px 0; }
.cta-box h2 { color: #fff; margin-bottom: 12px; }
.cta-box p { color: rgba(255,255,255,0.9); margin-bottom: 20px; }
.cta-box .btn-primary { background: #fff; color: var(--primary); }
.cta-box .btn-primary:hover { background: var(--gray-100); }

/* ---------- 博客列表 ---------- */
.post-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 24px; }
.post-card { background: #fff; border-radius: var(--radius-md); overflow: hidden; box-shadow: var(--shadow-sm); transition: var(--transition-base); display: flex; flex-direction: column; }
.post-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.post-card .post-thumb { height: 160px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); display: flex; align-items: center; justify-content: center; font-size: 40px; }
.post-card .post-body { padding: 20px; flex: 1; display: flex; flex-direction: column; }
.post-card .post-meta { font-size: 13px; color: var(--gray-400); margin-bottom: 8px; }
.post-card h3 { font-size: 17px; margin-bottom: 8px; }
.post-card p { font-size: 14px; color: var(--gray-500); margin-bottom: 14px; flex: 1; }
.post-card .read-more { font-size: 14px; font-weight: 500; }

/* ---------- 侧边栏 ---------- */
.layout-2col { display: grid; grid-template-columns: 1fr 300px; gap: 32px; align-items: start; }
.sidebar-card { background: #fff; border-radius: var(--radius-md); padding: 20px; box-shadow: var(--shadow-sm); margin-bottom: 20px; }
.sidebar-card h3 { font-size: 16px; margin-bottom: 12px; padding-bottom: 8px; border-bottom: 2px solid var(--gray-200); }
.sidebar-card ul { list-style: none; }
.sidebar-card li { margin-bottom: 8px; }
.sidebar-card a { font-size: 14px; color: var(--gray-600); }
.sidebar-card a:hover { color: var(--primary); }

/* ---------- Footer ---------- */
.site-footer { background: var(--gray-900); color: var(--gray-400); padding: 48px 0 24px; margin-top: 56px; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 32px; margin-bottom: 32px; }
.footer-col h4 { color: #fff; font-size: 15px; margin-bottom: 14px; }
.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: 8px; }
.footer-col a { color: var(--gray-400); font-size: 14px; }
.footer-col a:hover { color: #fff; }
.footer-brand p { font-size: 14px; line-height: 1.7; margin-top: 12px; }
.footer-bottom { border-top: 1px solid var(--gray-800); padding-top: 20px; text-align: center; font-size: 13px; }

/* ---------- 返回顶部 ---------- */
.back-top { position: fixed; right: 24px; bottom: 24px; width: 44px; height: 44px; border-radius: 50%; background: var(--primary); color: #fff; display: flex; align-items: center; justify-content: center; cursor: pointer; box-shadow: var(--shadow-lg); opacity: 0; visibility: hidden; transition: var(--transition-base); border: none; font-size: 20px; padding: 0; z-index: 900; }
.back-top.show { opacity: 1; visibility: visible; }
.back-top:hover { background: var(--primary-dark); }

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .layout-2col { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 768px) {
  :root { --header-h: 56px; }
  .nav-menu { display: none; position: absolute; top: var(--header-h); left: 0; right: 0; background: #fff; flex-direction: column; padding: 12px 20px; border-bottom: 1px solid var(--gray-200); box-shadow: var(--shadow-md); gap: 0; }
  .nav-menu.open { display: flex; }
  .nav-menu a { padding: 12px 14px; width: 100%; border-radius: 0; }
  .nav-toggle { display: block; }
  .hero { padding: 36px 0 28px; }
  .hero h1 { font-size: 26px; }
  .hero .lead { font-size: 15px; }
  h1 { font-size: 26px; }
  h2 { font-size: 22px; }
  .card { padding: 20px; }
  .upload-box { height: 200px; }
  .range-wrap { min-width: 100%; }
  .time-group input { width: 100%; }
  .section { padding: 32px 0; }
  .footer-grid { grid-template-columns: 1fr; gap: 24px; }
  .cta-box { padding: 28px 20px; }
  .step { gap: 14px; }
  .step-num { width: 36px; height: 36px; font-size: 16px; }
}