/* ==========================================================================
   Square Foot Calculator - 全站样式表
   采用 Mobile-First 设计，遵循 WCAG AA 无障碍与 Core Web Vitals 硬性指标
   ========================================================================== */

/* ---------- 1. CSS 变量 ---------- */
:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #eff6ff;
  --color-accent: #10b981;
  --color-accent-dark: #059669;

  --color-text: #111827;
  --color-text-secondary: #4b5563;
  --color-text-muted: #6b7280;
  --color-border: #e5e7eb;
  --color-border-strong: #d1d5db;
  --color-bg: #ffffff;
  --color-bg-alt: #f9fafb;
  --color-bg-card: #ffffff;

  --color-success: #10b981;
  --color-error: #ef4444;
  --color-warning: #f59e0b;
  --color-info: #3b82f6;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 1px 3px rgba(0, 0, 0, 0.08), 0 4px 16px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.08), 0 4px 10px rgba(0, 0, 0, 0.05);

  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
               'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'Fira Code', 'SF Mono', Menlo, Consolas, monospace;

  --container-max: 1200px;
  --container-reading: 760px;

  --header-height: 64px;
}

/* ---------- 2. 基础 Reset ---------- */
*, *::before, *::after { box-sizing: border-box; }

html {
  font-size: 16px;
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-body);
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, svg, video, canvas { max-width: 100%; height: auto; display: block; }

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 0.75em;
  line-height: 1.25;
  font-weight: 700;
  color: var(--color-text);
}
h1 { font-size: clamp(1.75rem, 4.5vw, 2.5rem); }
h2 { font-size: clamp(1.4rem, 3vw, 1.75rem); margin-top: 1.75rem; }
h3 { font-size: clamp(1.1rem, 2.2vw, 1.25rem); margin-top: 1.25rem; }

p { margin: 0 0 1rem; }

a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
  transition: color 0.15s;
}
a:hover { color: var(--color-primary-dark); }
a:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 2px;
}

ul, ol { padding-left: 1.5rem; margin: 0 0 1rem; }
li { margin-bottom: 0.35em; }

code {
  font-family: var(--font-mono);
  background: var(--color-primary-light);
  padding: 0.1em 0.35em;
  border-radius: 4px;
  font-size: 0.92em;
}

hr {
  border: 0;
  height: 1px;
  background: var(--color-border);
  margin: 2rem 0;
}

/* 跳转主内容链接（无障碍） */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-primary);
  color: #fff;
  padding: 8px 16px;
  z-index: 1000;
  text-decoration: none;
}
.skip-link:focus { top: 0; }

/* 隐藏文本但保留可访问性（屏幕阅读器和 SEO 可见） */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- 3. 布局容器 ---------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1rem;
}
@media (min-width: 640px) {
  .container { padding: 0 1.5rem; }
}
.container-reading { max-width: var(--container-reading); }

/* ---------- 4. 站点头部 / 导航 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--color-border);
  min-height: var(--header-height);
}
.main-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  height: var(--header-height);
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1rem;
}
@media (min-width: 640px) {
  .main-nav { padding: 0 1.5rem; }
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-text);
  text-decoration: none;
}
.logo:hover { color: var(--color-primary); }
.logo-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  border-radius: var(--radius-sm);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 0.9rem;
}

.nav-links {
  list-style: none;
  padding: 0;
  margin: 0;
  display: none;
  gap: 0.25rem;
  align-items: center;
}
@media (min-width: 1024px) {
  .nav-links { display: flex; }
}
.nav-links a,
.nav-links .dropdown-btn {
  display: inline-block;
  padding: 0.5rem 0.75rem;
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  border-radius: var(--radius-sm);
  background: none;
  border: none;
  cursor: pointer;
  font-family: inherit;
}
.nav-links a:hover,
.nav-links .dropdown-btn:hover { background: var(--color-primary-light); color: var(--color-primary); }

.dropdown { position: relative; }
.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 220px;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: 0.5rem;
  list-style: none;
  margin: 0;
  display: none;
  z-index: 50;
}
.dropdown[aria-expanded="true"] .dropdown-menu,
.dropdown:hover .dropdown-menu,
.dropdown:focus-within .dropdown-menu { display: block; }
.dropdown-menu a { display: block; padding: 0.5rem 0.75rem; border-radius: var(--radius-sm); }

.menu-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 48px;
  min-height: 48px;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
}
@media (min-width: 1024px) {
  .menu-toggle { display: none; }
}
.menu-toggle svg { width: 24px; height: 24px; stroke: var(--color-text); }

/* 移动端抽屉菜单 */
.mobile-menu {
  display: none;
  border-top: 1px solid var(--color-border);
  background: #fff;
}
.mobile-menu.open { display: block; }
.mobile-menu ul { list-style: none; padding: 0.5rem; margin: 0; }
.mobile-menu a {
  display: block;
  padding: 0.75rem 1rem;
  color: var(--color-text);
  text-decoration: none;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  min-height: 48px;
  display: flex;
  align-items: center;
}
.mobile-menu a:hover { background: var(--color-primary-light); color: var(--color-primary); }
.mobile-menu .submenu-title {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.75rem 1rem 0.25rem;
}

/* ---------- 5. Hero 区域 ---------- */
.hero {
  padding: 1.25rem 0 0.5rem;
  background: linear-gradient(180deg, var(--color-primary-light) 0%, var(--color-bg) 100%);
}
@media (min-width: 768px) {
  .hero { padding: 1.75rem 0 0.75rem; }
}
.hero h1 { margin-bottom: 0.5rem; }
.hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.1rem);
  color: var(--color-text-secondary);
  max-width: 720px;
  margin-bottom: 0.75rem;
}

/* ---------- 6. 计算器卡片 ---------- */
.calculator-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  margin: 0.5rem 0 1.25rem;
  box-shadow: var(--shadow-md);
  /* 预留最小高度防止 CLS */
  min-height: 480px;
}
@media (min-width: 640px) {
  .calculator-card { padding: 1.75rem; }
}

/* 形状选择 Tab */
.shape-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  padding: 0.35rem;
  background: var(--color-bg-alt);
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
}
.tab-btn {
  flex: 1 1 auto;
  min-width: 90px;
  min-height: 48px;
  padding: 0.5rem 0.75rem;
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  transition: background 0.15s, color 0.15s;
}
.tab-btn:hover { background: rgba(255, 255, 255, 0.8); color: var(--color-primary); }
.tab-btn.active {
  background: #fff;
  color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}
.tab-btn svg { width: 22px; height: 22px; }
.tab-btn:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

/* 输入区 */
.calc-body { display: grid; grid-template-columns: 1fr; gap: 1.5rem; }
@media (min-width: 900px) {
  .calc-body { grid-template-columns: 1.1fr 1fr; align-items: start; }
}

.calc-inputs { display: flex; flex-direction: column; gap: 1rem; }
.input-group {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.5rem;
  align-items: end;
}
.input-group label {
  grid-column: 1 / -1;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 0.1rem;
}
.input-group .help-text {
  grid-column: 1 / -1;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: 0.15rem;
}

input[type="number"],
input[type="text"],
select {
  font-size: 16px; /* 防 iOS 自动缩放 */
  min-height: 48px;
  padding: 0.65rem 0.85rem;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: #fff;
  color: var(--color-text);
  width: 100%;
  font-family: inherit;
  transition: border-color 0.15s, box-shadow 0.15s;
}
select {
  min-width: 90px;
  padding-right: 2rem;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='none' stroke='%236b7280' stroke-width='2' stroke-linecap='round' stroke-linejoin='round' d='M3 4.5l3 3 3-3'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
}
input:focus, select:focus {
  border-color: var(--color-primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}
input:invalid:not(:placeholder-shown) { border-color: var(--color-error); }
input[aria-invalid="true"] { border-color: var(--color-error); }

.input-error {
  color: var(--color-error);
  font-size: 0.82rem;
  margin-top: 0.25rem;
  display: none;
}
.input-error.show { display: block; }

/* 选项折叠区（损耗、价格） */
.calc-options {
  border-top: 1px solid var(--color-border);
  padding-top: 1rem;
  margin-top: 0.5rem;
}
.calc-options summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--color-primary);
  padding: 0.5rem 0;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.35rem;
}
.calc-options summary::-webkit-details-marker { display: none; }
.calc-options summary::before {
  content: "▸";
  transition: transform 0.15s;
  font-size: 0.8em;
}
.calc-options[open] summary::before { transform: rotate(90deg); }

.waste-presets {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.35rem;
}
.waste-preset {
  padding: 0.5rem 0.85rem;
  min-height: 40px;
  background: var(--color-bg-alt);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-secondary);
}
.waste-preset.active,
.waste-preset:hover {
  background: var(--color-primary-light);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

/* 结果区 */
.calc-result {
  background: linear-gradient(135deg, var(--color-primary-light) 0%, #f0fdf4 100%);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
  /* 预留结果区高度防 CLS */
  min-height: 220px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.result-primary { display: flex; align-items: baseline; justify-content: center; gap: 0.5rem; flex-wrap: wrap; }
.result-value {
  font-size: clamp(2.25rem, 7vw, 3.75rem);
  font-weight: 800;
  color: var(--color-accent-dark);
  line-height: 1;
  letter-spacing: -0.02em;
}
.result-unit {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-secondary);
}
.result-label {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}
.result-conversions {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 0.5rem;
  margin-top: 1.25rem;
  padding-top: 1rem;
  border-top: 1px dashed var(--color-border-strong);
}
.conv-item {
  background: rgba(255, 255, 255, 0.7);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.25rem;
}
.conv-value { font-weight: 700; color: var(--color-text); font-size: 1.05rem; display: block; }
.conv-label { font-size: 0.75rem; color: var(--color-text-muted); text-transform: uppercase; }

.result-waste {
  margin-top: 0.75rem;
  padding-top: 0.75rem;
  border-top: 1px dashed var(--color-border-strong);
  font-size: 0.95rem;
  color: var(--color-text-secondary);
}
.result-waste strong { color: var(--color-accent-dark); font-size: 1.1em; }

/* Canvas 可视化 */
.canvas-wrap {
  position: relative;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
  aspect-ratio: 5 / 3;
  min-height: 240px;
  overflow: hidden;
}
.canvas-wrap canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

/* 操作按钮 */
.calc-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1.25rem;
}
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-height: 48px;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1.5px solid transparent;
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  text-decoration: none;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.btn-primary {
  background: var(--color-primary);
  color: #fff;
  flex: 1 1 180px;
}
.btn-primary:hover { background: var(--color-primary-dark); color: #fff; }
.btn-secondary {
  background: #fff;
  color: var(--color-primary);
  border-color: var(--color-primary);
}
.btn-secondary:hover { background: var(--color-primary-light); }
.btn-ghost {
  background: transparent;
  color: var(--color-text-secondary);
}
.btn-ghost:hover { background: var(--color-bg-alt); color: var(--color-text); }
.btn:focus-visible { outline: 3px solid var(--color-primary); outline-offset: 2px; }

/* 多矩形（irregular / multi-room）行 */
.row-list { display: flex; flex-direction: column; gap: 0.5rem; }
.row-item {
  display: grid;
  grid-template-columns: 1fr 1fr auto;
  gap: 0.35rem;
  align-items: center;
}
.row-item input { min-height: 44px; }
.row-remove {
  min-width: 44px;
  min-height: 44px;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--color-error);
  font-size: 1.2rem;
}
.row-remove:hover { background: #fee2e2; border-color: var(--color-error); }

/* ---------- 7. 内容卡片 / 工具网格 ---------- */
.section { padding: 2rem 0; }
@media (min-width: 768px) { .section { padding: 3rem 0; } }
.section-alt { background: var(--color-bg-alt); }

.tools-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.85rem;
  margin: 1rem 0 1.5rem;
}
@media (min-width: 560px) {
  .tools-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 960px) {
  .tools-grid { grid-template-columns: repeat(3, 1fr); }
}
/* 对只有 4 个 card 的相关工具区，保持 4 列会更对称 */
.tools-grid--4 { grid-template-columns: 1fr; }
@media (min-width: 560px) { .tools-grid--4 { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 960px) { .tools-grid--4 { grid-template-columns: repeat(4, 1fr); } }
.tool-card {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  padding: 1rem 1.1rem;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: var(--color-text);
  transition: transform 0.15s, border-color 0.15s, box-shadow 0.15s;
  min-height: 110px;
}
.tool-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  color: var(--color-text);
}
.tool-card .icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--color-primary-light);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary);
}
.tool-card h3 {
  margin: 0.25rem 0 0;
  font-size: 1.05rem;
  font-weight: 700;
}
.tool-card p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

/* ---------- 8. FAQ ---------- */
.faq-list { display: flex; flex-direction: column; gap: 0.75rem; margin: 1.5rem 0; }
.faq-item {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 0;
  overflow: hidden;
}
.faq-item summary {
  list-style: none;
  cursor: pointer;
  padding: 1rem 1.25rem;
  font-weight: 600;
  font-size: 1rem;
  color: var(--color-text);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  min-height: 48px;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  font-size: 1.5rem;
  line-height: 1;
  color: var(--color-primary);
  font-weight: 400;
  flex-shrink: 0;
}
.faq-item[open] summary::after { content: "–"; }
.faq-item .faq-body {
  padding: 0 1.25rem 1.25rem;
  color: var(--color-text-secondary);
}
.faq-item .faq-body p:last-child { margin-bottom: 0; }

/* ---------- 9. 表格 ---------- */
.table-wrap { overflow-x: auto; margin: 1rem 0; }
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
th, td {
  padding: 0.65rem 0.85rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}
th {
  background: var(--color-bg-alt);
  font-weight: 700;
  color: var(--color-text);
}
tr:hover td { background: var(--color-primary-light); }

/* ---------- 10. 面包屑 ---------- */
.breadcrumb {
  padding: 0.85rem 0;
  font-size: 0.875rem;
  color: var(--color-text-muted);
}
.breadcrumb ol {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  align-items: center;
}
.breadcrumb li { margin: 0; display: inline-flex; align-items: center; gap: 0.4rem; }
.breadcrumb li + li::before {
  content: "›";
  color: var(--color-text-muted);
}
.breadcrumb a { color: var(--color-text-secondary); text-decoration: none; }
.breadcrumb a:hover { color: var(--color-primary); text-decoration: underline; }
.breadcrumb [aria-current="page"] { color: var(--color-text); font-weight: 600; }

/* ---------- 11. 广告位 ----------
   默认完全隐藏，避免审核未通过期间出现空白占位。
   仅当 AdSense 真实填充（is-filled）后由 JS 显示。 */
.ad-slot-wrapper {
  width: 100%;
  margin: 0;
  text-align: center;
  display: none;
  overflow: hidden;
  background: var(--color-bg-alt);
  border-radius: var(--radius-sm);
}
.ad-slot-wrapper.is-filled {
  display: block;
  margin: 1.5rem 0;
  padding: 0.5rem;
}
.ad-slot-label {
  display: none;
  font-size: 0.72rem;
  color: var(--color-text-muted);
  padding: 0.35rem 0;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.ad-slot-wrapper.is-filled .ad-slot-label { display: block; }

/* ---------- 12. Cookie 同意条幅 ---------- */
.cookie-banner {
  position: fixed;
  left: 1rem;
  right: 1rem;
  bottom: 1rem;
  max-width: 680px;
  margin: 0 auto;
  padding: 1rem 1.25rem;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  z-index: 200;
  display: none;
  font-size: 0.92rem;
  line-height: 1.5;
}
.cookie-banner.show { display: block; }
.cookie-banner p { margin: 0 0 0.75rem; color: var(--color-text-secondary); }
.cookie-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: flex-end;
}
.cookie-actions .btn { flex: 1 1 auto; min-width: 110px; }
@media (min-width: 640px) {
  .cookie-actions .btn { flex: 0 1 auto; }
}

/* ---------- 13. Footer ---------- */
.site-footer {
  background: #0f172a;
  color: #cbd5e1;
  padding: 2.5rem 0 1.5rem;
  margin-top: 4rem;
  font-size: 0.92rem;
}
.site-footer h3 {
  color: #fff;
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.site-footer a {
  color: #cbd5e1;
  text-decoration: none;
  display: block;
  padding: 0.25rem 0;
}
.site-footer a:hover { color: #fff; text-decoration: underline; }
.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  margin-bottom: 2rem;
}
@media (min-width: 640px) {
  .footer-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 1024px) {
  .footer-grid { grid-template-columns: 1.5fr 1fr 1fr 1fr; }
}
.footer-brand p { color: #94a3b8; margin: 0; font-size: 0.9rem; line-height: 1.6; }
.footer-brand .logo { color: #fff; }
.footer-bottom {
  border-top: 1px solid #1e293b;
  padding-top: 1.25rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.75rem;
  color: #94a3b8;
  font-size: 0.85rem;
}

/* ---------- 14. 其他工具 ---------- */
.text-muted { color: var(--color-text-muted); }
.text-small { font-size: 0.875rem; }
.last-updated {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.82rem;
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
  padding: 0.2rem 0.55rem;
  border-radius: 999px;
  margin: 0.25rem 0 0;
}

.callout {
  background: var(--color-primary-light);
  border-left: 4px solid var(--color-primary);
  padding: 1rem 1.25rem;
  border-radius: var(--radius-sm);
  margin: 1.25rem 0;
}
.callout strong { color: var(--color-primary-dark); }

/* 响应式隐藏 */
.mobile-only { display: block; }
.desktop-only { display: none; }
@media (min-width: 1024px) {
  .mobile-only { display: none; }
  .desktop-only { display: block; }
}

/* ---------- 15. 单位换算器卡片 ---------- */
.converter-card {
  display: grid;
  gap: 1rem;
  align-items: center;
  grid-template-columns: 1fr;
  min-height: auto;
  padding: 1.75rem;
}
@media (min-width: 720px) {
  .converter-card { grid-template-columns: 1fr auto 1fr; }
}
.converter-row {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.converter-row label {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-text-secondary);
}
.converter-row input {
  font-size: 1.5rem;
  font-weight: 600;
  padding: 0.75rem 0.9rem;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  width: 100%;
  transition: border-color 0.15s;
}
.converter-row input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}
.converter-unit {
  color: var(--color-text-muted);
  font-size: 0.85rem;
  margin-top: 0.1rem;
}
.converter-equals {
  display: none;
  font-size: 2rem;
  color: var(--color-text-muted);
  text-align: center;
  font-weight: 300;
}
@media (min-width: 720px) {
  .converter-equals { display: block; }
}

/* ---------- 16. 发行方信息块 ---------- */
.publisher-info {
  font-style: normal;
  line-height: 1.6;
  background: var(--color-bg-alt);
  border-left: 3px solid var(--color-primary);
  padding: 0.85rem 1.1rem;
  border-radius: var(--radius-sm);
  margin: 1rem 0 1.5rem;
  color: var(--color-text-secondary);
}

/* ---------- 17. 友情链接 ---------- */
.friend-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem 1.25rem;
  margin: 1.5rem 0 0.5rem;
  padding: 0.75rem 1.25rem;
  background: var(--color-bg-alt);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
}
.friend-links__title {
  margin: 0;
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  flex-shrink: 0;
}
.friend-links__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem 1.25rem;
  list-style: none;
  padding: 0;
  margin: 0;
}
.friend-links__list li { margin: 0; }
.friend-links__list a {
  display: inline-flex;
  align-items: center;
  padding: 0.15rem 0;
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  text-decoration: none;
  border-bottom: 1px dashed transparent;
}
.friend-links__list a:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

/* 打印优化 */
@media print {
  .site-header, .site-footer, .ad-slot-wrapper, .cookie-banner,
  .calc-actions, .canvas-wrap { display: none !important; }
  .calculator-card { box-shadow: none; border: 1px solid #ccc; }
}