/* ===================================
   钢结构向导站 — 主题样式
   无框架依赖，纯 CSS 变量 + 基础类
   =================================== */

/* --- CSS 变量（全局） --- */
:root {
  /* ===== 品牌主色 — 信息蓝 ===== */
  --color-primary: #1A4480;
  --color-primary-dark: #143667;
  --color-primary-deep: #0E2547;
  --color-primary-light: #E7EEF6;
  --color-primary-lighter: #F2F6FB;

  /* ===== 中性色 ===== */
  --color-ink: #1A1A1A;
  --color-muted: #5C5C5C;
  --color-border: #E5E1D7;

  /* ===== 语义强调 ===== */
  --color-accent: #C0392B;
  --color-success: #4A7C59;
  --color-warning: #E0A800;

  /* ===== 背景与表面 ===== */
  --color-bg: #FBFAF7;
  --color-card: #FFFFFF;

  /* ===== 字体 ===== */
  --font-body: system-ui, -apple-system, 'Segoe UI', Roboto, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-heading: system-ui, -apple-system, 'Segoe UI', Roboto, 'PingFang SC', 'Microsoft YaHei', sans-serif;

  /* ===== 布局 ===== */
  --container-max: 1200px;
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-full: 9999px;
}

/* --- 基础重置 --- */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-family: var(--font-body);
  color: var(--color-ink);
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  margin: 0;
  width: 100%;
  min-height: 100vh;
  background-color: var(--color-bg);
  line-height: 1.6;
}

/* --- 容器 --- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1rem;
}

@media (min-width: 768px) {
  .container {
    padding: 0 2rem;
  }
}

/* ===================================
   组件类
   =================================== */

/* --- 按钮 --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 2rem;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 1rem;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-decoration: none;
  transition: background 0.2s, box-shadow 0.2s;
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
}

.btn-block {
  width: 100%;
}

/* --- 卡片 --- */
.card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: box-shadow 0.2s, transform 0.2s;
}

.card:hover {
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.08);
  transform: translateY(-2px);
}

/* --- 标签 --- */
.tag {
  display: inline-block;
  padding: 0.125rem 0.5rem;
  font-size: 0.75rem;
  font-weight: 500;
  border-radius: var(--radius-full);
  background: var(--color-primary-light);
  color: var(--color-primary);
}

/* --- 选项卡片（选择器） --- */
.option-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  padding: 1rem;
  border-radius: var(--radius-lg);
  border: 2px solid #e5e7eb;
  background: #fff;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.2s;
}

.option-card:hover {
  border-color: color-mix(in srgb, var(--color-primary) 40%, transparent);
  background: var(--color-primary-lighter);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.option-card.selected {
  border-color: var(--color-primary);
  background: var(--color-primary-lighter);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.06);
}

/* --- 输入框 --- */
.input {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid #e5e7eb;
  border-radius: var(--radius-lg);
  font-family: var(--font-body);
  font-size: 1rem;
  background: #fff;
  transition: border-color 0.2s;
}

.input:focus {
  outline: none;
  border-color: var(--color-primary);
}

/* --- 导航栏 --- */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.8);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid color-mix(in srgb, var(--color-border) 60%, transparent);
}

/* --- 淡入动画 --- */
.fade-slide-in {
  animation: fadeSlideIn 0.3s ease-out;
}

@keyframes fadeSlideIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===================================
   页脚（所有页面统一）
   =================================== */
.footer { background:#2C3E50;color:#999;font-size:14px;flex-shrink:0; }
.cta-row { text-align:center;padding:16px 0;border-bottom:1px solid rgba(255,255,255,.08);font-size:20px;font-weight:700;color:#fff; }
.footer-grid { display:grid;grid-template-columns:1fr;gap:16px;padding:20px 0 16px; }
@media (min-width:768px) { .footer-grid { grid-template-columns:1.5fr 1fr; } }
.footer-left .footer-logo { display:flex;align-items:center;gap:8px;margin-bottom:8px; }
.footer-left .footer-logo span { color:#fff;font-weight:600;font-size:15px; }
.footer-left p { margin:0;line-height:1.6;font-size:13px; }
.footer-right { display:flex;flex-direction:column;gap:6px;font-size:13px; }
.footer-bottom { border-top:1px solid rgba(255,255,255,.08);text-align:center;padding:10px 0;font-size:12px;color:#666; }