@charset "UTF-8";

/* ===== 基础重置 ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

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

body {
  font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: #333333;
  background-color: #ECF0F1;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  border: 0;
  vertical-align: middle;
}

a {
  color: #E67E22;
  text-decoration: none;
  transition: color 0.3s ease;
}

a:hover {
  color: #d35400;
  text-decoration: underline;
}

ul, ol {
  list-style: none;
}

h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  color: #2C3E50;
}

p {
  margin-bottom: 1em;
}

/* ===== CSS变量 ===== */
:root {
  --primary: #2C3E50;
  --secondary: #E67E22;
  --dark: #1A252F;
  --light: #ECF0F1;
  --text: #333333;
  --text-light: #666666;
  --border: #BDC3C7;
  --white: #FFFFFF;
}

/* ===== 工具类 ===== */
.clearfix::after {
  content: "";
  display: table;
  clear: both;
}

.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.hidden { display: none; }
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.flex {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
}

.flex-wrap {
  -webkit-flex-wrap: wrap;
  -ms-flex-wrap: wrap;
  flex-wrap: wrap;
}

.justify-between {
  -webkit-box-pack: justify;
  -webkit-justify-content: space-between;
  -ms-flex-pack: justify;
  justify-content: space-between;
}

.justify-center {
  -webkit-box-pack: center;
  -webkit-justify-content: center;
  -ms-flex-pack: center;
  justify-content: center;
}

.align-center {
  -webkit-box-align: center;
  -webkit-align-items: center;
  -ms-flex-align: center;
  align-items: center;
}

/* ===== 动画 ===== */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-30px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes countUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.animate-fadeIn {
  animation: fadeIn 0.8s ease forwards;
}

.animate-slideUp {
  animation: slideUp 0.8s ease forwards;
}

/* ===== 返回顶部按钮 ===== */
.back-to-top {
  position: fixed;
  bottom: 40px;
  right: 40px;
  width: 48px;
  height: 48px;
  background: var(--secondary);
  color: var(--white);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 20px;
  z-index: 999;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -webkit-align-items: center;
  -ms-flex-align: center;
  align-items: center;
  -webkit-box-pack: center;
  -webkit-justify-content: center;
  -ms-flex-pack: center;
  justify-content: center;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background: #d35400;
  transform: translateY(-3px);
}