/* ==========================================================================
   格子·AI进化论 — 全站样式
   设计系统：赛博青绿暗色科技风
   ========================================================================== */

/* ---------- 设计变量 ---------- */
:root {
  /* 色彩系统 */
  --bg:            #0a0e1a;   /* 深蓝黑基底 */
  --surface:       #111827;   /* 卡片/表面 */
  --surface-2:     #161f30;   /* 次级表面（hover 等） */
  --accent:        #00ffd0;   /* 霓虹青 主强调 */
  --accent-2:      #00d4ff;   /* 电光蓝 次强调/渐变 */
  --accent-dim:    rgba(0, 255, 208, 0.12);
  --accent-glow:   rgba(0, 255, 208, 0.35);
  --text:          #e6edf3;   /* 正文 */
  --text-muted:    #8b949e;   /* 次要文字 */
  --text-dim:      #6b7480;   /* 更暗 */
  --border:        rgba(0, 255, 208, 0.15);
  --border-strong: rgba(0, 255, 208, 0.3);

  /* 字体栈（全系统字体，零网络依赖） */
  --font-sans: system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "JetBrains Mono", "Fira Code", "Cascadia Code", Menlo, Consolas, monospace;

  /* 间距 */
  --container: 1100px;
  --radius: 10px;
  --radius-sm: 6px;
}

/* ---------- 重置 ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 16px;
  min-height: 100vh;
  overflow-x: hidden;
}
img { max-width: 100%; display: block; }
a { color: var(--accent); text-decoration: none; transition: color .2s, opacity .2s; }
a:hover { opacity: .85; }
ul { list-style: none; }

/* 网格背景 motif —— 全站统一的品牌视觉符号 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(0, 255, 208, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 255, 208, 0.035) 1px, transparent 1px);
  background-size: 44px 44px;
  pointer-events: none;
  z-index: 0;
}

/* 主内容层在网格之上 */
main, header, footer { position: relative; z-index: 1; }

/* ---------- 通用工具类 ---------- */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}
.gradient-text {
  background: linear-gradient(120deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.mono { font-family: var(--font-mono); }
.center { text-align: center; }

/* ==========================================================================
   导航栏
   ========================================================================== */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 14, 26, 0.82);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  text-shadow: 0 0 16px var(--accent-glow);
}
.brand-mark {
  width: 26px; height: 26px;
  flex-shrink: 0;
}
.brand:hover { opacity: 1; }
.brand span { color: var(--accent); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
}
.nav-links a {
  color: var(--text-muted);
  font-size: .95rem;
  font-weight: 500;
  position: relative;
  padding: 4px 0;
}
.nav-links a:hover { color: var(--accent); opacity: 1; }
.nav-links a.active { color: var(--accent); }
.nav-links a.active::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: -4px;
  height: 2px;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent-glow);
}

/* 移动端汉堡菜单 */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}
.nav-toggle span {
  width: 22px; height: 2px;
  background: var(--text);
  transition: .3s;
  border-radius: 2px;
}
.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); }

@media (max-width: 720px) {
  .nav-toggle { display: flex; }
  .nav-links {
    position: absolute;
    top: 64px; left: 0; right: 0;
    flex-direction: column;
    background: rgba(10, 14, 26, 0.98);
    border-bottom: 1px solid var(--border);
    padding: 16px 24px 24px;
    gap: 16px;
    transform: translateY(-150%);
    transition: transform .3s ease;
    backdrop-filter: blur(12px);
  }
  .nav-links.open { transform: translateY(0); }
}

/* ==========================================================================
   按钮
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 26px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: .95rem;
  font-family: var(--font-mono);
  cursor: pointer;
  transition: all .25s;
  border: 1px solid transparent;
}
.btn-primary {
  background: linear-gradient(120deg, var(--accent), var(--accent-2));
  color: #04121a;
  box-shadow: 0 0 20px var(--accent-glow);
}
.btn-primary:hover {
  opacity: 1;
  transform: translateY(-2px);
  box-shadow: 0 6px 28px var(--accent-glow);
}
.btn-ghost {
  background: transparent;
  color: var(--text);
  border-color: var(--border-strong);
}
.btn-ghost:hover { opacity: 1; border-color: var(--accent); color: var(--accent); }

/* ==========================================================================
   首页 Hero
   ========================================================================== */
.hero {
  position: relative;
  padding: 90px 0 70px;
  text-align: center;
  overflow: hidden;
}
/* 动态扫描线 */
.hero::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  opacity: .6;
  animation: scan 6s linear infinite;
}
@keyframes scan {
  0%   { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}
/* hero 径向光晕 */
.hero::after {
  content: "";
  position: absolute;
  top: 50%; left: 50%;
  width: 700px; height: 700px;
  transform: translate(-50%, -50%);
  background: radial-gradient(circle, rgba(0,255,208,0.08), transparent 60%);
  pointer-events: none;
}

.terminal-prompt {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: .9rem;
  margin-bottom: 24px;
  display: inline-block;
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: rgba(0,255,208,0.04);
}
.terminal-prompt .blink {
  animation: blink 1s steps(1) infinite;
}
@keyframes blink { 50% { opacity: 0; } }

.hero h1 {
  font-size: clamp(2.4rem, 7vw, 4.4rem);
  font-weight: 800;
  letter-spacing: -1px;
  margin-bottom: 22px;
  line-height: 1.1;
  text-shadow: 0 0 40px var(--accent-glow);
}
.hero-tagline {
  font-size: clamp(1.05rem, 2.5vw, 1.35rem);
  color: var(--text-muted);
  margin-bottom: 20px;
  min-height: 1.6em;
  font-family: var(--font-mono);
}
.hero-tagline .cursor {
  display: inline-block;
  width: 3px;
  height: 1.1em;
  background: var(--accent);
  vertical-align: text-bottom;
  margin-left: 2px;
  animation: blink 1s steps(1) infinite;
  box-shadow: 0 0 8px var(--accent-glow);
}
/* 使命宣言——首页第一屏核心主张 */
.hero-mission {
  font-size: clamp(1rem, 2.2vw, 1.2rem);
  color: var(--text);
  margin: 0 0 32px;
  padding: 16px 28px;
  border-left: 3px solid var(--accent);
  background: var(--accent-dim);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  display: inline-block;
  text-align: left;
  max-width: 620px;
  line-height: 1.8;
  box-shadow: inset 0 0 30px rgba(0,255,208,0.04);
}
.hero-mission strong {
  color: var(--accent);
  font-weight: 600;
}
.hero-cta {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ==========================================================================
   通用区段
   ========================================================================== */
.section {
  padding: 64px 0;
}
.section-head {
  margin-bottom: 40px;
}
.section-head h2 {
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  font-weight: 700;
  margin-bottom: 10px;
}
.section-head .eyebrow {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: .85rem;
  letter-spacing: 2px;
  text-transform: uppercase;
  margin-bottom: 8px;
  display: block;
}
.section-head p {
  color: var(--text-muted);
  max-width: 620px;
}
.section-head.center { text-align: center; }
.section-head.center p { margin: 0 auto; }

/* ==========================================================================
   文章卡片网格
   ========================================================================== */
.post-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(310px, 1fr));
  gap: 24px;
}
.post-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 26px;
  transition: all .25s;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}
.post-card::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .3s;
}
.post-card:hover {
  border-color: var(--border-strong);
  transform: translateY(-4px);
  background: var(--surface-2);
}
.post-card:hover::before { transform: scaleX(1); }
.post-card h3 {
  font-size: 1.18rem;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 10px;
}
.post-card h3 a { color: var(--text); }
.post-card h3 a:hover { color: var(--accent); opacity: 1; }
.post-card p {
  color: var(--text-muted);
  font-size: .94rem;
  margin-bottom: 18px;
  flex: 1;
}
.post-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: .82rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
  margin-top: auto;
}

/* 标签 */
.tag {
  display: inline-block;
  padding: 3px 11px;
  font-size: .75rem;
  font-family: var(--font-mono);
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid var(--border);
  border-radius: 999px;
  white-space: nowrap;
}

.tags-row { display: flex; flex-wrap: wrap; gap: 8px; }

/* ==========================================================================
   首页置顶文章（创刊号大卡片）
   ========================================================================== */
.featured {
  padding: 56px 0 24px;
}
.featured-card {
  position: relative;
  background: linear-gradient(135deg, var(--surface) 0%, var(--surface-2) 100%);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  padding: 40px;
  overflow: hidden;
  transition: all .3s;
}
.featured-card::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
}
.featured-card::after {
  content: "";
  position: absolute;
  top: -60px; right: -60px;
  width: 200px; height: 200px;
  background: radial-gradient(circle, var(--accent-dim), transparent 70%);
  pointer-events: none;
}
.featured-card:hover { transform: translateY(-3px); box-shadow: 0 12px 40px rgba(0,0,0,0.4); }
.featured-badges { margin-bottom: 18px; display: flex; gap: 8px; flex-wrap: wrap; }
.featured-badges .badge {
  font-family: var(--font-mono);
  font-size: .75rem;
  padding: 4px 12px;
  border-radius: 999px;
  border: 1px solid var(--border-strong);
}
.featured-badges .badge.star { color: var(--accent); background: var(--accent-dim); }
.featured-badges .badge.plain { color: var(--text-muted); background: var(--surface); }
.featured-card h2 {
  font-size: clamp(1.5rem, 3.5vw, 2rem);
  font-weight: 800;
  margin-bottom: 14px;
  line-height: 1.3;
}
.featured-card h2 a { color: var(--text); }
.featured-card h2 a:hover { color: var(--accent); opacity: 1; }
.featured-card .featured-excerpt {
  color: var(--text-muted);
  font-size: 1.02rem;
  margin-bottom: 22px;
  max-width: 680px;
}
.featured-meta {
  display: flex;
  gap: 20px;
  align-items: center;
  font-family: var(--font-mono);
  font-size: .85rem;
  color: var(--text-dim);
  flex-wrap: wrap;
}
.featured-meta .read-cta {
  margin-left: auto;
  color: var(--accent);
  font-weight: 600;
}
@media (max-width: 600px) {
  .featured-card { padding: 28px 22px; }
  .featured-meta .read-cta { margin-left: 0; }
}
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

/* ==========================================================================
   博客列表页 —— 标签筛选栏
   ========================================================================== */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 40px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}
.filter-chip {
  padding: 7px 18px;
  font-size: .88rem;
  font-family: var(--font-mono);
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  cursor: pointer;
  transition: all .2s;
}
.filter-chip:hover { color: var(--accent); border-color: var(--border-strong); }
.filter-chip.active {
  background: var(--accent);
  color: #04121a;
  border-color: var(--accent);
  font-weight: 600;
}

/* 列表项式卡片（博客页用，比网格更紧凑） */
.post-list-card {
  display: flex;
  gap: 28px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px 28px;
  margin-bottom: 18px;
  transition: all .25s;
}
.post-list-card:hover {
  border-color: var(--border-strong);
  background: var(--surface-2);
}
.post-list-card .date-block {
  flex-shrink: 0;
  font-family: var(--font-mono);
  color: var(--accent);
  min-width: 90px;
}
.post-list-card .date-block .month { font-size: .8rem; }
.post-list-card .date-block .day { font-size: 1.7rem; font-weight: 700; line-height: 1; }
.post-list-card .date-block .year { font-size: .75rem; color: var(--text-dim); }
.post-list-card .content { flex: 1; }
.post-list-card h3 { font-size: 1.2rem; margin-bottom: 8px; }
.post-list-card h3 a { color: var(--text); }
.post-list-card h3 a:hover { color: var(--accent); opacity: 1; }
.post-list-card .excerpt { color: var(--text-muted); font-size: .94rem; margin: 10px 0 14px; }
.post-list-card .meta-row {
  display: flex; gap: 16px; align-items: center;
  font-size: .82rem; color: var(--text-dim); font-family: var(--font-mono);
}

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  display: none;
}

@media (max-width: 600px) {
  .post-list-card { flex-direction: column; gap: 12px; }
}

/* ==========================================================================
   文章正文页
   ========================================================================== */
.article-wrap {
  max-width: 760px;
  margin: 0 auto;
  padding: 56px 24px 80px;
}
.article-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: .9rem;
  margin-bottom: 32px;
}
.article-back:hover { color: var(--accent); opacity: 1; }
.article-header { margin-bottom: 40px; padding-bottom: 28px; border-bottom: 1px solid var(--border); }
.article-header h1 {
  font-size: clamp(1.8rem, 5vw, 2.6rem);
  font-weight: 800;
  line-height: 1.25;
  margin: 14px 0;
}
.article-header .tags-row { margin-top: 18px; }
.article-meta-line {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  font-family: var(--font-mono);
  font-size: .85rem;
  color: var(--text-muted);
  margin-top: 4px;
}
.article-meta-line span { display: inline-flex; align-items: center; gap: 6px; }

/* 正文排版 */
.prose { font-size: 1.06rem; line-height: 1.85; color: var(--text); }
.prose h2 {
  font-size: 1.6rem; font-weight: 700; margin: 48px 0 18px;
  padding-left: 14px; border-left: 3px solid var(--accent);
}
.prose h3 { font-size: 1.25rem; font-weight: 600; margin: 34px 0 12px; }
.prose p { margin-bottom: 20px; }
.prose ul, .prose ol { margin: 0 0 20px; padding-left: 24px; }
.prose li { margin-bottom: 8px; }
.prose ul li::marker { color: var(--accent); }
.prose ol li::marker { color: var(--accent); font-weight: 600; }
.prose strong { color: #fff; }
.prose blockquote {
  border-left: 3px solid var(--accent);
  background: var(--accent-dim);
  padding: 14px 20px;
  margin: 24px 0;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text);
}
.prose blockquote p { margin-bottom: 0; }
.prose a { text-decoration: underline; text-underline-offset: 3px; }
.prose code {
  font-family: var(--font-mono);
  font-size: .9em;
  background: rgba(0,255,208,0.08);
  color: var(--accent);
  padding: 2px 7px;
  border-radius: 4px;
  border: 1px solid var(--border);
}
.prose pre {
  background: #060a12;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 22px;
  overflow-x: auto;
  margin: 24px 0;
  font-size: .9rem;
  line-height: 1.6;
}
.prose pre code {
  background: none; border: none; padding: 0; color: var(--text);
}
.prose img { border-radius: var(--radius); border: 1px solid var(--border); margin: 24px 0; }
.prose hr { border: none; border-top: 1px solid var(--border); margin: 40px 0; }

/* 文末作者卡片 */
.author-card {
  display: flex;
  gap: 18px;
  align-items: center;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin: 48px 0 32px;
}
.author-card .avatar {
  width: 60px; height: 60px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700; font-size: 1.5rem;
  color: #04121a; flex-shrink: 0;
}
.author-card h4 { font-size: 1.05rem; margin-bottom: 4px; }
.author-card p { color: var(--text-muted); font-size: .9rem; margin: 0; }

/* 上下篇导航 */
.post-nav {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  margin-top: 24px;
  padding-top: 28px;
  border-top: 1px solid var(--border);
  flex-wrap: wrap;
}
.post-nav a {
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: .9rem;
  max-width: 48%;
}
.post-nav a:hover { color: var(--accent); opacity: 1; }
.post-nav .label { display: block; font-size: .75rem; color: var(--text-dim); margin-bottom: 4px; }

/* ==========================================================================
   关于页
   ========================================================================== */
.about-wrap {
  max-width: 780px;
  margin: 0 auto;
  padding: 56px 24px 80px;
}
.about-hero {
  display: flex;
  gap: 36px;
  align-items: center;
  margin-bottom: 56px;
  flex-wrap: wrap;
}
.about-hero .avatar-lg {
  width: 130px; height: 130px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700; font-size: 3.2rem;
  color: #04121a; flex-shrink: 0;
  box-shadow: 0 0 40px var(--accent-glow);
}
.about-hero h1 { font-size: clamp(2rem, 5vw, 2.8rem); margin-bottom: 10px; }
.about-hero .tagline { color: var(--text-muted); font-family: var(--font-mono); font-size: 1.05rem; }

.about-section { margin-bottom: 48px; }
.about-section h2 {
  font-size: 1.4rem; margin-bottom: 18px;
  padding-left: 14px; border-left: 3px solid var(--accent);
}
.about-section p { color: var(--text-muted); margin-bottom: 16px; font-size: 1.02rem; }
.about-section p strong { color: var(--text); }

/* 技能标签云 */
.skill-cloud { display: flex; flex-wrap: wrap; gap: 12px; }
.skill-cloud .tag { font-size: .88rem; padding: 6px 16px; }

/* 未来计划卡片（课程/陪跑入口） */
.plan-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
  margin-top: 8px;
}
.plan-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: all .25s;
}
.plan-card:hover { border-color: var(--border-strong); transform: translateY(-3px); }
a.plan-card { color: inherit; display: block; }
.plan-card .icon { font-size: 1.8rem; margin-bottom: 12px; }
.plan-card h3 { font-size: 1.1rem; margin-bottom: 8px; }
.plan-card p { font-size: .9rem; color: var(--text-muted); margin: 0; }
.plan-card .status {
  display: inline-block; margin-top: 14px;
  font-family: var(--font-mono); font-size: .78rem;
  color: var(--accent); padding: 3px 10px;
  background: var(--accent-dim); border-radius: 999px;
}

/* 联系区 */
.contact-links { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 16px; }
.contact-links a {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 12px 22px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: .92rem;
  transition: all .2s;
}
.contact-links a:hover { border-color: var(--accent); color: var(--accent); opacity: 1; transform: translateY(-2px); }

@media (max-width: 600px) {
  .about-hero { flex-direction: column; text-align: center; }
}

/* ==========================================================================
   页脚
   ========================================================================== */
.footer {
  border-top: 1px solid var(--border);
  background: rgba(6, 10, 18, 0.6);
  padding: 48px 0 32px;
  margin-top: 40px;
}
.footer-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 32px;
  flex-wrap: wrap;
}
.footer-brand { max-width: 320px; }
.footer-brand .brand { margin-bottom: 12px; }
.footer-brand p { color: var(--text-muted); font-size: .9rem; }
.footer-social { display: flex; gap: 18px; }
.footer-social a {
  color: var(--text-muted);
  font-size: .9rem;
  font-family: var(--font-mono);
}
.footer-social a:hover { color: var(--accent); opacity: 1; }
.footer-bottom {
  max-width: var(--container);
  margin: 32px auto 0;
  padding: 20px 24px 0;
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--text-dim);
  font-size: .82rem;
  font-family: var(--font-mono);
}

/* ==========================================================================
   动画进场（淡入上移）
   ========================================================================== */
.fade-up {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity .7s ease, transform .7s ease;
}
.fade-up.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ==========================================================================
   返回顶部
   ========================================================================== */
.to-top {
  position: fixed;
  right: 24px; bottom: 24px;
  width: 44px; height: 44px;
  border-radius: 50%;
  background: var(--accent);
  color: #04121a;
  display: flex; align-items: center; justify-content: center;
  border: none; cursor: pointer;
  font-size: 1.2rem; font-weight: 700;
  box-shadow: 0 4px 20px var(--accent-glow);
  opacity: 0; visibility: hidden;
  transition: all .3s;
  z-index: 90;
}
.to-top.show { opacity: 1; visibility: visible; }
.to-top:hover { transform: translateY(-3px); }

/* ==========================================================================
   无障碍：减少动效偏好
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
    scroll-behavior: auto !important;
  }
}