:root {
  /* 冷银灰键帽风主色（深色默认背景上浮的银灰胶囊） */
  --aluminum: #cfd6dc;            /* 冷银高光 */
  --aluminum-mid: #aeb7bf;        /* 键帽中间 */
  --aluminum-low: #9aa4ad;        /* 阴影过渡 */
  --aluminum-edge: #dfe5ea;       /* 边缘亮线 */

  --gunmetal: #2b3338;
  --charcoal: #323a40;
  --dark-charcoal: #1e2326;

  --platinum: #e9edf0;
  --steel: #8b97a1;
  --dark-steel: #515c65;

  /* 基础变量 */
  --bg-color: var(--dark-charcoal);
  --surface: #24292c;             /* 基座/面板 */
  --text-color: var(--platinum);
  --text-muted: #acb5bc;
  --primary-color: var(--aluminum);

  /* 容器对齐 */
  --container-max: 1140px;        /* 收窄以形成更像键盘的排布 */
  --container-pad: 1rem;

  /* 键帽浮雕光影（顶部左高光+右下阴影） */
  --keycap-top-highlight: rgba(255, 255, 255, 0.75);
  --keycap-top-glow: rgba(255, 255, 255, 0.28);
  --keycap-bottom-shadow: rgba(0, 0, 0, 0.45);
  --keycap-bottom-deep: rgba(0, 0, 0, 0.65);

  /* 阴影系统（更克制） */
  --shadow-distance: 3px;
  --shadow-blur: 10px;
  --highlight: rgba(255, 255, 255, 0.12);
  --shadow-dark: rgba(0, 0, 0, 0.5);

  /* 圆角（胶囊） */
  --radius-lg: 999px;             /* 胶囊 */
  --radius-md: 999px;
  --radius-sm: 12px;

  /* 动效 */
  --transition-fast: 160ms;
  --transition-slow: 300ms;

  /* 视觉细节 */
  --border-color: rgba(210, 220, 228, 0.55);  /* 亮边 */
  --border-color-inner: rgba(0, 0, 0, 0.18);  /* 内侧暗线 */
  --focus-ring: 0 0 0 4px rgba(207, 214, 220, 0.18);
}

/* 跟随系统浅色 */
@media (prefers-color-scheme: light) {
  :root {
    --bg-color: #f2f4f6;
    --surface: #ffffff;
    --text-color: #1f2427;
    --text-muted: #58636d;

    --aluminum: #aeb7bf;
    --aluminum-mid: #cfd6dc;
    --aluminum-low: #a2adb6;
    --aluminum-edge: #f4f7f9;

    --keycap-top-highlight: rgba(255,255,255,0.95);
    --keycap-top-glow: rgba(255,255,255,0.5);
    --keycap-bottom-shadow: rgba(0,0,0,0.12);
    --keycap-bottom-deep: rgba(0,0,0,0.16);

    --border-color: rgba(158, 170, 182, 0.55);
    --border-color-inner: rgba(0, 0, 0, 0.06);
    --shadow-dark: rgba(0,0,0,0.12);
  }
}

/* 跟随系统色（浅色） */
@media (prefers-color-scheme: light) {
  :root {
    --bg-color: #f4f6f8;
    --card-bg-color: #ffffff;
    --text-color: #1f2427;
    --text-muted: #5b6670;
    --aluminum: #7c8a97;
    --steel: #8b99a6;
    --border-color: rgba(25, 35, 45, 0.12);
    --shadow-dark: rgba(0, 0, 0, 0.12);
    --highlight: rgba(255, 255, 255, 0.7);
  }
}

/* 精密机械风格加载动画（弱化纹理，提升纯净感） */
.loading-overlay {
  position: fixed;
  inset: 0;
  background: linear-gradient(135deg, rgba(31,36,39,0.96), rgba(37,44,48,0.96));
  backdrop-filter: saturate(110%) blur(1px);
  display: grid;
  place-items: center;
  z-index: 9999;
  transition: opacity 0.45s ease, visibility 0.45s ease;
}

.loading-overlay.hidden {
  opacity: 0;
  visibility: hidden;
}

.industrial-loader {
  position: relative;
  width: 120px;
  height: 120px;
}

.gear {
  position: absolute;
  width: 50px;
  height: 50px;
  background: transparent;
  border: 3px solid var(--aluminum);
  border-radius: 50%;
  box-shadow: 
    0 0 0 1px var(--dark-charcoal),
    inset 0 0 8px rgba(168, 168, 168, 0.4),
    0 0 15px rgba(168, 168, 168, 0.2);
  /* 拉丝金属质感 */
  background-image: 
    repeating-linear-gradient(
      135deg,
      rgba(168, 168, 168, 0.1) 0px,
      rgba(168, 168, 168, 0.1) 1px,
      transparent 1px,
      transparent 3px
    );
}

.gear::before {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 25px;
  height: 25px;
  background: var(--dark-charcoal);
  border: 2px solid var(--aluminum);
  border-radius: 50%;
  transform: translate(-50%, -50%);
  box-shadow: 
    inset 0 0 6px rgba(0, 0, 0, 0.5);
}

.gear::after {
  content: "";
  position: absolute;
  top: -6px;
  left: 50%;
  width: 8px;
  height: 18px;
  background: var(--aluminum);
  transform: translateX(-50%);
  border-radius: 2px;
  box-shadow: 
    0 35px 0 var(--aluminum),
    35px 0 0 var(--aluminum),
    0 -35px 0 var(--aluminum),
    0 0 10px rgba(168, 168, 168, 0.5);
}

.gear1 {
  top: 0;
  left: 0;
  animation: rotate1 5s linear infinite;
}

.gear2 {
  top: 0;
  right: 0;
  animation: rotate2 5s linear infinite;
}

.gear3 {
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  animation: rotate3 5s linear infinite;
}

@keyframes rotate1 {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

@keyframes rotate2 {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(-360deg); }
}

@keyframes rotate3 {
  0% { transform: translateX(-50%) rotate(0deg); }
  100% { transform: translateX(-50%) rotate(360deg); }
}

/* 拉丝金属质感 */
.metal-texture {
  background-image: 
    linear-gradient(
      135deg,
      rgba(255, 255, 255, 0.05) 25%,
      transparent 25%,
      transparent 50%,
      rgba(255, 255, 255, 0.05) 50%,
      rgba(255, 255, 255, 0.05) 75%,
      transparent 75%,
      transparent
    );
  background-size: 4px 4px;
}

/* 高光和阴影效果 */
.industrial-shadow-out {
  box-shadow: 
    var(--shadow-distance) var(--shadow-distance) var(--shadow-blur) var(--shadow-dark),
    calc(var(--shadow-distance) * -1) calc(var(--shadow-distance) * -1) var(--shadow-blur) var(--highlight);
}

.industrial-shadow-in {
  box-shadow: 
    inset var(--shadow-distance) var(--shadow-distance) var(--shadow-blur) var(--shadow-dark),
    inset calc(var(--shadow-distance) * -1) calc(var(--shadow-distance) * -1) var(--shadow-blur) var(--highlight);
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
  margin: 0;
  padding: 0;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.65;
  /* 背景简化：去除重复斜纹，只保留柔和渐变 */
  background-image:
    radial-gradient(1200px 600px at 50% -10%, rgba(255,255,255,0.03), transparent 60%),
    linear-gradient(135deg, rgba(44,54,60,0.28), rgba(27,32,35,0.28));
  background-blend-mode: overlay, normal;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 0.45s ease, transform 0.45s ease;
}

header {
  background: transparent;
  padding: 2rem;
  text-align: center;
  position: relative;
  margin-bottom: 1.5rem;
}

header h1 {
  font-size: 2.6rem;
  font-weight: 800;
  color: var(--platinum);
  margin: 0;
  text-transform: uppercase;
  letter-spacing: 2px;
  position: relative;
  display: inline-block;
  padding: 0.75rem 1.6rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: linear-gradient(145deg, rgba(53,64,74,0.65), rgba(31,36,39,0.65));
  backdrop-filter: saturate(110%);
  box-shadow: 0 6px 16px var(--shadow-dark);
  text-shadow: 0 1px 1px rgba(0,0,0,0.35);
}

/* 精密机械框架装饰 */
header h1::before,
header h1::after {
  content: "";
  position: absolute;
  width: 24px;
  height: 24px;
  border-color: var(--steel);
  border-style: solid;
}

header h1::before {
  top: -8px;
  left: -8px;
  border-width: 3px 0 0 3px;
  box-shadow: 
    inset -2px -2px 4px rgba(0, 0, 0, 0.4),
    1px 1px 2px rgba(255, 255, 255, 0.1);
}

header h1::after {
  bottom: -8px;
  right: -8px;
  border-width: 0 3px 3px 0;
  box-shadow: 
    inset 2px 2px 4px rgba(0, 0, 0, 0.4),
    -1px -1px 2px rgba(255, 255, 255, 0.1);
}

/* 顶部导航容器（与键盘托盘呼应的细边基座） */
nav {
  background: linear-gradient(180deg, rgba(255,255,255,0.02), transparent);
  position: sticky;
  top: 0;
  z-index: 1000;
  padding: 0.8rem 0;
  display: flex;
  justify-content: center;
  margin-bottom: 1.6rem;
  border-bottom: 1px solid rgba(255,255,255,0.06);
  backdrop-filter: saturate(110%);
}

nav .nav-wrap {
  max-width: var(--container-max);
  padding: 0 var(--container-pad);
  margin: 0 auto;
  width: 100%;
  display: flex;
  justify-content: center;
  text-align: center;
}

nav ul {
  list-style-type: none;
  padding: 0;
  margin: 0 auto;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: nowrap;              /* 强制单行 */
  gap: 0.5rem;                    /* 适度减小间距以容纳单行 */
  width: 100%;
  max-width: var(--container-max);
  overflow-x: auto;               /* 小屏时允许横向滚动，保持单行 */
  scrollbar-width: thin;
}

nav li {
  margin: 0;
  white-space: nowrap;            /* 防止换行 */
}

/* 顶部导航也采用“扁薄键帽”胶囊 */
nav a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--text-color);
  text-decoration: none;
  font-size: 0.98rem;
  font-weight: 700;
  padding: 0.55rem 1.1rem;
  border-radius: var(--radius-md);
  transition: transform var(--transition-fast) ease, box-shadow var(--transition-fast) ease, background var(--transition-fast) ease, color var(--transition-fast) ease, border-color var(--transition-fast) ease;
  position: relative;
  overflow: hidden;
  min-width: 112px;
  text-align: center;

  background: linear-gradient(180deg, var(--aluminum-edge), var(--aluminum-mid));
  border: 1px solid var(--border-color);
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 -1px 0 var(--border-color-inner),
    0 -4px 12px var(--keycap-top-glow),
    5px 8px 14px var(--keycap-bottom-shadow);
  text-shadow: 0 1px 0 rgba(255,255,255,0.45);
}

/* 悬停/激活 */
nav a:hover {
  transform: translateY(-2px);
  color: #2e3a42;
  background: linear-gradient(180deg, var(--aluminum-edge), var(--aluminum));
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 -1px 0 rgba(0,0,0,0.1),
    0 -6px 16px var(--keycap-top-glow),
    8px 12px 20px var(--keycap-bottom-deep);
}

nav a.active, nav a[aria-current="page"], nav a[aria-current="true"] {
  background: linear-gradient(180deg, var(--aluminum-mid), var(--aluminum-low));
  color: #2e3a42;
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 1px 0 rgba(255,255,255,0.45),
    4px 6px 12px var(--keycap-bottom-shadow);
  transform: translateY(0px);
  text-shadow: 0 1px 0 rgba(255,255,255,0.45);
}

/* 去除强烈扫光，改为柔和高光 */
nav a::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(255,255,255,0.05), transparent 40%);
  opacity: 0.7;
  transition: opacity 0.4s ease;
  pointer-events: none;
}

nav a:hover::before {
  left: 100%;
}

main {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 1rem;
}

.category-title {
  font-size: 1.9rem;
  font-weight: 800;
  margin: 2rem 0 1.4rem;
  color: var(--platinum);
  text-transform: uppercase;
  letter-spacing: 1.2px;
  position: relative;
  padding-bottom: 0.6rem;
  text-align: center;
  text-shadow: 0 1px 0 rgba(255,255,255,0.2);
}

.category-title::after {
  content: "";
  display: block;
  width: 88px;
  height: 3px;
  background: linear-gradient(90deg, var(--aluminum-edge), var(--aluminum));
  margin: 0.6rem auto;
  border-radius: 999px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.18);
}

/* 键盘阵列：等距网格，固定行高，行列间隙等距 */
.link-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;                      /* 等距如键盘缝隙 */
  margin-bottom: 2.6rem;
  align-items: stretch;
}

/* 冷银灰键帽胶囊 */
.link-card {
  position: relative;
  background: linear-gradient(180deg, var(--aluminum-edge), var(--aluminum-mid));
  border-radius: var(--radius-md);
  padding: 1rem 0.9rem;
  text-align: center;
  transition: transform var(--transition-fast) ease, box-shadow var(--transition-fast) ease, background var(--transition-fast) ease, border-color var(--transition-fast) ease;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 112px;
  overflow: hidden;

  /* 外轮廓：上亮线+下暗线的立体边 */
  border: 1px solid var(--border-color);
  box-shadow:
    /* 顶部左高光边 */
    -1px -1px 0 var(--aluminum-edge),
    /* 内侧微暗线 */
    inset 0 -1px 0 var(--border-color-inner),
    /* 漫反射顶光晕 */
    0 -6px 16px var(--keycap-top-glow),
    /* 右下投影 */
    6px 10px 18px var(--keycap-bottom-shadow);
}

.link-card:hover {
  transform: translateY(-3px);
  background: linear-gradient(180deg, var(--aluminum-edge), var(--aluminum));
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 -1px 0 rgba(0,0,0,0.12),
    0 -8px 22px var(--keycap-top-glow),
    10px 14px 26px var(--keycap-bottom-deep);
}

/* 明确鼠标移开时恢复到默认配色与阴影（优先级覆盖可能的内联样式） */
.link-card:not(:hover):not(:active) {
  background: linear-gradient(180deg, var(--aluminum-edge), var(--aluminum-mid)) !important;
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 -1px 0 var(--border-color-inner),
    0 -6px 16px var(--keycap-top-glow),
    6px 10px 18px var(--keycap-bottom-shadow) !important;
  transform: translateY(0) !important;
}

.link-card:active,
.link-card:has(a:active) {
  transform: translateY(-1px);
  background: linear-gradient(180deg, var(--aluminum-mid), var(--aluminum-low));
  box-shadow:
    -1px -1px 0 var(--aluminum-edge),
    inset 0 1px 0 rgba(255,255,255,0.3),
    6px 10px 18px var(--keycap-bottom-shadow);
}

.link-card a {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  text-decoration: none;
  z-index: 12;
  display: block;
}

.link-card i {
  font-size: 1.9rem;
  margin-bottom: 0.8rem;
  color: #6f7a84;
  text-shadow: 0 1px 1px rgba(255, 255, 255, 0.35), 0 1px 2px rgba(0,0,0,0.2);
  transition: transform var(--transition-fast) ease, text-shadow var(--transition-fast) ease, color var(--transition-fast) ease;
  position: relative;
  z-index: 11;
}

.link-card:hover i {
  transform: translateY(-1px) scale(1.08);
  color: #e6ecf1;
  text-shadow:
    0 1px 0 rgba(255,255,255,0.35),
    0 2px 6px rgba(0, 0, 0, 0.36);
}

.link-card h3 {
  font-size: 0.98rem;                 /* 略增字号提升清晰度 */
  margin: 0;
  color: var(--text-color);
  line-height: 1.4;                   /* 提升行高改善可读性 */
  font-weight: 700;                   /* 增强字重以提高边界清晰度 */
  max-width: 100%;
  height: 2.8em;                      /* 与行高匹配，避免裁切 */
  overflow: hidden;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  line-clamp: 2;
  -webkit-box-orient: vertical;
  text-overflow: ellipsis;
  white-space: normal;
  padding: 0 0.5rem;                  /* 微调内边距避免贴边 */
  position: relative;
  z-index: 11;
  text-shadow:
    0 1px 0 rgba(255,255,255,0.45),   /* 底层浅色描边提升对比 */
    0 0 1px rgba(0,0,0,0.35);         /* 细微暗缘避免高光背景吞字 */
}

/* Hover 时文本更清晰：色彩、描边与对比增强 */
.link-card:hover h3 {
  color: #f3f6f8;                     /* 更明亮的前景色 */
  text-shadow:
    0 1px 0 rgba(255,255,255,0.6),    /* 提升立体亮边 */
    0 0 1px rgba(0,0,0,0.45),
    0 2px 6px rgba(0,0,0,0.18);       /* 轻微发光避免背景干扰 */
  transform: translateY(-1px);
  transition: color var(--transition-fast) ease, text-shadow var(--transition-fast) ease, transform var(--transition-fast) ease;
}

footer {
  background: transparent;
  color: var(--steel);
  text-align: center;
  padding: 2.2rem 1.2rem;
  font-size: 0.92rem;
  border-top: 1px solid var(--border-color);
  margin-top: 2.6rem;
  background-image: none;
}

footer nav {
  margin-top: 1.5rem;
  background-color: transparent;
}

footer nav a {
  color: var(--steel);
  margin: 0 0.8rem;
  font-size: 0.88rem;
  display: inline-block;
  padding: 0.5rem 1rem;
  border-radius: 12px;
  background: linear-gradient(145deg, rgba(53,64,74,0.6), rgba(31,36,39,0.6));
  border: 1px solid var(--border-color);
  box-shadow: 0 3px 8px var(--shadow-dark);
  transition: transform var(--transition-fast) ease, box-shadow var(--transition-fast) ease, background var(--transition-fast) ease;
  text-shadow: 0 1px 1px rgba(0, 0, 0, 0.25);
}

footer nav a:hover {
  transform: translateY(-2px);
  color: var(--aluminum);
  background: linear-gradient(145deg, rgba(62,74,84,0.68), rgba(31,36,39,0.75));
  box-shadow: 0 5px 12px var(--shadow-dark);
}

/* 响应式设计 */
@media (max-width: 1200px) {
  :root {
    --container-max: 95vw;
  }
  main {
    padding: 1rem;
    max-width: var(--container-max);
  }
  .link-grid {
    grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
    gap: 1.2rem;
  }
}

@media (max-width: 768px) {
  html {
    font-size: 15px;
  }

  main {
    padding: 0.8rem;
  }

  .link-grid {
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 1rem;
  }

  nav {
    padding: 0.6rem;                /* 小屏顶部导航更紧凑 */
  }

  nav a {
    padding: 0.7rem 1.2rem;
    font-size: 0.9rem;
    min-width: 100px;
  }

  .category-title {
    font-size: 1.6rem;
    margin: 2rem 0 1.2rem;
  }

  .link-card {
    padding: 1.2rem 0.8rem;
    min-height: 100px;
  }

  .link-card i {
    font-size: 1.8rem;
    margin-bottom: 0.8rem;
  }

  .link-card h3 {
    font-size: 0.9rem;                /* 小屏也提升一点字号 */
    height: 2.6em;
  }
}

@media (max-width: 480px) {
  html {
    font-size: 14px;
  }

  main {
    padding: 0.6rem;
  }

  .link-grid {
    grid-template-columns: repeat(auto-fill, minmax(90px, 1fr));
    gap: 0.8rem;
  }

  header h1 {
    font-size: 1.8rem;
    padding: 0.4rem 1rem;
  }

  nav ul {
    gap: 0.6rem;
  }

  nav a {
    padding: 0.5rem 0.8rem;         /* 小屏进一步收紧保持单行 */
    font-size: 0.84rem;
  }

  .category-title {
    font-size: 1.4rem;
    margin: 1.8rem 0 1rem;
  }

  .link-card {
    padding: 1rem 0.6rem;
    min-height: 90px;
  }

  .link-card i {
    font-size: 1.6rem;
    margin-bottom: 0.6rem;
  }

  .link-card h3 {
    font-size: 0.85rem;               /* 极小屏保持可读性 */
    padding: 0 0.28rem;
    height: 2.5em;
  }

  footer {
    padding: 1.5rem 0.8rem;
  }

  footer nav a {
    margin: 0 0.5rem;
    font-size: 0.75rem;
    padding: 0.4rem 0.8rem;
  }
}

@media (max-width: 360px) {
  html {
    font-size: 13px;
  }

  .link-grid {
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: 0.7rem;
  }

  header h1 {
    font-size: 1.6rem;
    padding: 0.3rem 0.8rem;
  }

  nav a {
    padding: 0.5rem 0.8rem;
    font-size: 0.8rem;
    min-width: 80px;
  }

  .link-card {
    padding: 0.8rem 0.5rem;
    min-height: 80px;
  }

  .link-card i {
    font-size: 1.4rem;
    margin-bottom: 0.5rem;
  }

  .link-card h3 {
    font-size: 0.8rem;                /* 超小屏也略增字号 */
    padding: 0 0.2rem;
    height: 2.3em;
  }
}

/* 工业风格装饰元素（弱化存在感） */
.industrial-decoration {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: -1;
  overflow: hidden;
  opacity: 0.2;
}

.gear-decoration {
  position: absolute;
  border: 2px solid rgba(192, 192, 192, 0.1);
  border-radius: 50%;
  opacity: 0.3;
}

.gear-decoration::before {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 50%;
  height: 50%;
  background: transparent;
  border: 1px solid rgba(192, 192, 192, 0.1);
  border-radius: 50%;
  transform: translate(-50%, -50%);
}

.gear-large {
  top: 5%;
  right: 5%;
  width: 110px;
  height: 110px;
  animation: rotate 40s linear infinite;
}

.gear-medium {
  bottom: 10%;
  left: 5%;
  width: 72px;
  height: 72px;
  animation: rotate 28s linear infinite reverse;
}

.gear-small {
  top: 20%;
  left: 15%;
  width: 44px;
  height: 44px;
  animation: rotate 24s linear infinite;
}

@keyframes rotate {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}