/*
 * =======================================
 *  base.css — 教师教育学院官网公共样式
 *  配色：师大蓝（参考北京师范大学）
 *  用途：全局变量、Reset、通用组件、响应式基础
 *  说明：所有页面均需引入此文件
 *  版本：v3.0 重构（响应式断点集中管理）
 * =======================================
 */

/* ===== DESIGN TOKENS - 师大蓝（参考北京师范大学） ===== */
:root {
  /* 主色系：师大蓝（从官网提取） */
  --navy-900: #002F5F;
  --navy-800: #003A75;
  --navy-700: #0050A5;
  --navy-600: #0D58AA;
  --navy-500: #1A73C7;
  --navy-400: #4A9AE8;
  --navy-300: #7CB8F0;
  --navy-200: #B0D4F5;
  --navy-100: #CCE1FA;
  --navy-50: #E8F1FF;

  /* 强调色：师大朱红（官网按钮/标签色） */
  --gold-600: #B33A2A;
  --gold-500: #DF4C36;
  --gold-400: #E8684F;
  --gold-300: #F09080;
  --gold-200: #F7BAB0;
  --gold-100: #FDE0DA;

  --white: #ffffff;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;

  --red-500: #dc2626;
  --green-500: #16a34a;

  --font-display: "Noto Serif SC", "Source Han Serif CN", "STSong", "SimSun", serif;
  --font-body: "Noto Sans SC", "Source Han Sans CN", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", monospace;

  --shadow-sm: 0 1px 2px rgba(0, 47, 95, 0.04);
  --shadow-md: 0 4px 16px rgba(0, 47, 95, 0.08);
  --shadow-lg: 0 8px 32px rgba(0, 47, 95, 0.12);
  --shadow-xl: 0 16px 48px rgba(0, 47, 95, 0.16);

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

  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);

  /* 响应式断点（仅在JS中读取，CSS中仍使用硬编码值保持兼容） */
  --bp-tablet: 1024px;
  --bp-mobile: 768px;
}

/* ===== RESET & BASE ===== */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box;}
html { scroll-behavior: smooth; font-size: 16px; }
body {
  font-family: var(--font-body);
  color: var(--gray-800);
  background: linear-gradient(180deg, #ffffff 0%, #E8F1FF 50%, #CCE1FA 100%);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}
a { text-decoration: none; color: inherit; transition: color var(--transition-fast); }
img { max-width: 100%; display: block; }
ul, ol { list-style: none; }

/* ===== UTILITY ===== */
.container { max-width: 1280px; margin: 0 auto; padding: 0 32px; }
.section-label {
  font-family: var(--font-body);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 3px;
  text-transform: uppercase;
  color: var(--gold-600);
  margin-bottom: 8px;
}
.section-title {
  font-family: var(--font-display);
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 700;
  color: var(--navy-800);
  line-height: 1.3;
  margin-bottom: 16px;
  position: relative;
  display: inline-block;
}
.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--gold-500), var(--navy-500), var(--navy-400));
  border-radius: 4px;
  margin-top: 12px;
}
.section-desc {
  font-size: 16px;
  color: var(--gray-500);
  max-width: 560px;
  line-height: 1.8;
}
.more-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  font-weight: 600;
  color: var(--navy-600);
  margin-top: 16px;
  transition: all var(--transition-fast);
}
.more-link:hover { color: var(--gold-500); gap: 10px; }
.more-link svg { width: 16px; height: 16px; transition: transform var(--transition-fast); }
.more-link:hover svg { transform: translateX(2px); }

/* ===== ANIMATIONS ===== */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes slideInLeft {
  from { opacity: 0; transform: translateX(-40px); }
  to { opacity: 1; transform: translateX(0); }
}
@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.95); }
  to { opacity: 1; transform: scale(1); }
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}
@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}
.animate-on-scroll {
  opacity: 0;
  transform: translateY(30px);
  transition: all 0.7s cubic-bezier(0.4, 0, 0.2, 1);
}
.animate-on-scroll.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== TOP BAR ===== */
.top-bar {
  background: var(--navy-900);
  color: var(--navy-300);
  font-size: 13px;
  padding: 8px 0;
  position: relative;
  z-index: 100;
}
.top-bar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.top-bar a { color: var(--navy-300); }
.top-bar a:hover { color: var(--gold-400); }
.top-bar-links { display: flex; gap: 20px; align-items: center; }
.top-bar-links span { color: var(--navy-600); }

/* ===== HEADER ===== */
.header {
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid rgba(0, 47, 95, 0.06);
  position: sticky;
  top: 0;
  z-index: 90;
  transition: box-shadow var(--transition-base);
}
.header.scrolled { box-shadow: 0 4px 20px rgba(0, 47, 95, 0.08); }
.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}
.logo { display: flex; align-items: center; gap: 14px; }
.logo-icon {
  width: 44px; height: 44px;
  background: linear-gradient(135deg, var(--navy-700), var(--navy-500));
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  color: white;
  font-family: var(--font-display);
  font-size: 28px;
  font-weight: 700;
  flex-shrink: 0;
}
.logo-text { display: flex; flex-direction: column; }
.logo-text .cn {
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 700;
  color: var(--navy-800);
  letter-spacing: 2px;
}
.logo-text .en {
  font-size: 11px;
  color: var(--gray-400);
  letter-spacing: 1px;
  font-weight: 500;
}

/* ===== Desktop Nav ===== */
.main-nav { display: flex; align-items: center; gap: 4px; }
.main-nav a {
  font-size: 15px;
  font-weight: 500;
  color: var(--gray-600);
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  position: relative;
}
.main-nav a:hover, .main-nav a.active {
  color: var(--navy-700);
  background: var(--navy-50);
}
.main-nav a.active::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 16px;
  right: 16px;
  height: 2px;
  background: var(--gold-500);
  border-radius: 2px;
}
.header-actions { display: flex; align-items: center; gap: 12px; }
.search-btn {
  width: 40px; height: 40px;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
  background: transparent;
  color: var(--gray-500);
}
.search-btn:hover {
  border-color: var(--navy-300);
  color: var(--navy-600);
  background: var(--navy-50);
}
.search-btn svg { width: 18px; height: 18px; }
.search-btn.is-open {
  background: var(--navy-700);
  border-color: var(--navy-700);
  color: var(--white);
}

/* ===== Search Panel ===== */
.search-panel {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background: var(--white);
  border-top: 1px solid var(--gray-100);
  box-shadow: 0 12px 40px rgba(0, 47, 95, 0.12);
  z-index: 89;
  padding: 0;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transform: translateY(-8px);
  transition: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  pointer-events: none;
}
.search-panel.is-open {
  max-height: 200px;
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
  padding: 20px 0;
}
.search-panel .container {
  display: flex;
  align-items: center;
  gap: 12px;
}
.search-panel input {
  flex: 1;
  height: 48px;
  padding: 0 20px;
  border: 2px solid var(--gray-200);
  border-radius: 100px;
  font-size: 15px;
  color: var(--gray-800);
  background: var(--gray-50);
  outline: none;
  transition: all var(--transition-fast);
  font-family: var(--font-body);
}
.search-panel input::placeholder {
  color: var(--gray-400);
}
.search-panel input:focus {
  border-color: var(--navy-400);
  background: var(--white);
  box-shadow: 0 0 0 4px rgba(13, 88, 170, 0.1);
}
.search-submit-btn {
  height: 48px;
  padding: 0 28px;
  border: none;
  border-radius: 100px;
  background: linear-gradient(135deg, var(--navy-600), var(--navy-500));
  color: var(--white);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
  font-family: var(--font-body);
}
.search-submit-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(13, 88, 170, 0.3);
}
.search-submit-btn svg { width: 16px; height: 16px; }
.search-panel .search-hint {
  font-size: 12px;
  color: var(--gray-400);
  flex-shrink: 0;
}
.search-panel .search-shortcut {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-left: 8px;
}
.search-panel .search-shortcut kbd {
  padding: 2px 6px;
  border: 1px solid var(--gray-200);
  border-radius: 4px;
  background: var(--white);
  font-size: 11px;
  color: var(--gray-400);
  font-family: var(--font-mono);
}

/* ===== Search Overlay ===== */
.search-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 47, 95, 0.4);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 88;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
}
.search-overlay.is-open {
  opacity: 1;
  pointer-events: auto;
}

/* ===== Mobile Menu Toggle (Hamburger) ===== */
.menu-toggle {
  display: none;
  width: 40px; height: 40px;
  border: none; background: transparent;
  cursor: pointer;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  position: relative;
  z-index: 101;
}
.menu-toggle span {
  width: 22px; height: 2px;
  background: var(--navy-700);
  border-radius: 2px;
  transition: all var(--transition-base);
  transform-origin: center;
}
/* Hamburger → X animation */
.menu-toggle.is-open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.menu-toggle.is-open span:nth-child(2) {
  opacity: 0;
  transform: scaleX(0);
}
.menu-toggle.is-open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ===== Mobile Menu Overlay ===== */
.mobile-nav-overlay {
  display: none;              /* shown via JS toggle */
  position: fixed;
  inset: 0;
  background: rgba(0, 47, 95, 0.5);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 95;
  opacity: 0;
  transition: opacity var(--transition-base);
}
.mobile-nav-overlay.is-open {
  opacity: 1;
}

/* ===== Mobile Navigation Panel ===== */
.mobile-nav-panel {
  display: none;              /* shown via JS toggle */
  position: fixed;
  top: 0;
  right: -320px;              /* off-screen right */
  width: 300px;
  max-width: 85vw;
  height: 100vh;
  background: var(--white);
  z-index: 100;
  padding: 80px 24px 32px;
  box-shadow: -8px 0 32px rgba(0, 47, 95, 0.15);
  overflow-y: auto;
  transition: right var(--transition-base);
}
.mobile-nav-panel.is-open {
  right: 0;
}
.mobile-nav-panel .panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--gray-100);
}
.mobile-nav-panel .panel-header .logo {
  gap: 10px;
}
.mobile-nav-panel .panel-header .logo-icon {
  width: 36px; height: 36px;
  font-size: 16px;
}
.mobile-nav-panel .panel-header .logo-text .cn {
  font-size: 15px;
}
.mobile-nav-panel .panel-header .logo-text .en {
  font-size: 10px;
}
.mobile-nav-close {
  width: 36px; height: 36px;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-sm);
  background: transparent;
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  color: var(--gray-500);
  transition: all var(--transition-fast);
}
.mobile-nav-close:hover {
  background: var(--gray-50);
  border-color: var(--gray-300);
  color: var(--gray-700);
}
.mobile-nav-close svg { width: 18px; height: 18px; }
.mobile-nav-panel nav {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.mobile-nav-panel nav a {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  font-size: 16px;
  font-weight: 500;
  color: var(--gray-700);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}
.mobile-nav-panel nav a:hover {
  background: var(--navy-50);
  color: var(--navy-600);
}
.mobile-nav-panel nav a.active {
  background: linear-gradient(135deg, var(--navy-50), var(--navy-100));
  color: var(--navy-700);
  font-weight: 700;
  border-left: 3px solid var(--navy-600);
}
.mobile-nav-panel nav a svg {
  width: 20px; height: 20px;
  color: var(--gray-400);
  flex-shrink: 0;
}
.mobile-nav-panel nav a.active svg {
  color: var(--navy-600);
}
.mobile-nav-panel .panel-footer {
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--gray-100);
}
.mobile-nav-panel .panel-footer a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 0;
  font-size: 14px;
  color: var(--gray-500);
}
.mobile-nav-panel .panel-footer a:hover { color: var(--navy-600); }

/* ===== BREADCRUMB（面包屑导航） ===== */
.breadcrumb-bar {
  background: var(--white);
  border-bottom: 1px solid var(--gray-100);
  padding: 14px 0;
}
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--gray-400);
}
.breadcrumb a {
  color: var(--gray-500);
  transition: color var(--transition-fast);
}
.breadcrumb a:hover { color: var(--navy-600); }
.breadcrumb .current { color: var(--navy-700); font-weight: 600; }
.breadcrumb .sep { color: var(--gray-300); }

/* ===== FOOTER ===== */
.footer {
  background: linear-gradient(180deg, #002F5F 0%, #001A3A 100%);
  padding: 60px 0 0;
}
.footer-main {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  padding-bottom: 48px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}
.footer-brand .logo { margin-bottom: 16px; }
.footer-brand .logo .cn { color: var(--white); }
.footer-brand .logo .en { color: var(--navy-300); }
.footer-brand .logo .logo-icon {
  background: linear-gradient(135deg, var(--navy-600), var(--navy-500));
}
.footer-brand p {
  font-size: 14px;
  color: var(--navy-400);
  line-height: 1.8;
  margin-bottom: 20px;
}
.footer-social { display: flex; gap: 12px; }
.footer-social a {
  width: 36px; height: 36px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.06);
  display: flex; align-items: center; justify-content: center;
  color: var(--navy-400);
  font-size: 16px;
  transition: all var(--transition-fast);
}
.footer-social a:hover { background: var(--gold-500); color: var(--navy-900); }
.footer-column h4 {
  font-size: 14px;
  font-weight: 600;
  color: var(--white);
  margin-bottom: 20px;
  letter-spacing: 1px;
}
.footer-column ul { display: flex; flex-direction: column; gap: 12px; }
.footer-column li a {
  font-size: 14px;
  color: var(--navy-400);
  transition: all var(--transition-fast);
}
.footer-column li a:hover { color: var(--gold-400); padding-left: 4px; }
.footer-bottom {
  padding: 20px 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.footer-bottom p { font-size: 13px; color: var(--navy-500); }
.footer-bottom a { color: var(--navy-400); }
.footer-bottom a:hover { color: var(--gold-400); }

/* ==========================================================================
 *  RESPONSIVE — 所有断点统一管理
 *  断点说明：
 *    Tablet:  max-width: 1024px  (iPad 横屏、小笔记本)
 *    Mobile:  max-width:  768px  (手机竖屏)
 *  各页面独有布局的响应式规则仍保留在各自CSS文件中，
 *  此处仅包含全局组件（header/footer/container/top-bar 等）的响应式规则。
 * ========================================================================== */

/* --- Tablet: <= 1024px --- */
@media (max-width: 1024px) {
  /* Footer: 2 columns */
  .footer-main { grid-template-columns: 1fr 1fr; }
  .footer-bottom {
    flex-direction: column;
    gap: 8px;
    text-align: center;
  }
}

/* --- Mobile: <= 768px --- */
@media (max-width: 768px) {
  /* Container: narrow padding */
  .container { padding: 0 20px; }

  /* Top bar: hide secondary links */
  .top-bar-links:last-child { display: none; }

  /* Header: shorter height */
  .header .container { height: 60px; }

  /* Desktop nav: hide, show hamburger */
  .main-nav { display: none; }
  .menu-toggle { display: flex; }

  /* Mobile nav: show */
  .mobile-nav-overlay,
  .mobile-nav-panel { display: block; }
  /* Initial hidden state */
  .mobile-nav-overlay {
    pointer-events: none;
  }
  .mobile-nav-overlay.is-open {
    pointer-events: auto;
  }

  /* Footer: single column */
  .footer-main { grid-template-columns: 1fr; gap: 32px; }
  .footer { padding: 40px 0 0; }

  /* Back to top: smaller on mobile */
  .back-to-top { right: 20px; bottom: 24px; width: 40px; height: 40px; }
}

/* ===== Back to Top 悬浮按钮 ===== */
.back-to-top {
  position: fixed;
  right: 32px;
  bottom: 200px;
  width: 46px;
  height: 46px;
  background: rgba(0,47,95,0.55);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  color: var(--white, #fff);
  border: 1px solid rgba(255,255,255,0.18);
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease, background 0.25s ease, border-color 0.25s ease;
  z-index: 900;
  box-shadow: 0 4px 16px rgba(0,47,95,0.18);
  line-height: 1;
  overflow: hidden;
}
.back-to-top::before {
  content: '';
  width: 10px;
  height: 10px;
  border-right: 2.5px solid var(--white, #fff);
  border-top: 2.5px solid var(--white, #fff);
  transform: rotate(-45deg);
  margin-top: 3px;
  opacity: 0.95;
  transition: transform 0.25s ease, opacity 0.25s ease;
}
.back-to-top:hover {
  background: rgba(0,47,95,0.75);
  border-color: rgba(255,255,255,0.3);
  transform: translateY(0);
  box-shadow: 0 6px 22px rgba(0,47,95,0.3);
}
.back-to-top:hover::before {
  transform: rotate(-45deg) translate(1px, -1px);
  opacity: 1;
}
.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

/* ===== Icon (SVG img) 通用图标尺寸 ===== */
img.icon {
  display: inline-block;
  vertical-align: middle;
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}
img.icon-sm { width: 14px; height: 14px; }
img.icon-md { width: 18px; height: 18px; }
img.icon-lg { width: 24px; height: 24px; }