/* ========== 基础与变量 ========== */
:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-bg: #f8fafc;
  --color-bg-alt: #fff;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --container: min(100% - 32px, 720px);
  --header-h: 56px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

/* ========== 按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  font-size: 15px;
  font-weight: 600;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.2s, transform 0.15s;
}

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

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

.btn-block {
  width: 100%;
}

/* ========== 头部 ========== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-h);
  background: var(--color-bg-alt);
  box-shadow: 0 1px 0 rgba(0,0,0,0.06);
  z-index: 100;
}

.header-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 16px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 17px;
  font-weight: 700;
  color: var(--color-primary);
}

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
  position: relative;
}

.nav-toggle::before,
.nav-toggle::after {
  content: "";
  position: absolute;
  left: 10px;
  right: 10px;
  height: 2px;
  background: var(--color-text);
  transition: transform 0.2s;
}

.nav-toggle::before {
  top: 14px;
}

.nav-toggle::after {
  bottom: 14px;
}

.nav-toggle[aria-expanded="true"]::before {
  transform: translateY(6px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"]::after {
  transform: translateY(-6px) rotate(-45deg);
}

.nav {
  display: flex;
  gap: 24px;
}

.nav a {
  font-size: 15px;
  color: var(--color-text);
  font-weight: 500;
}

.nav a:hover {
  color: var(--color-primary);
}

/* ========== Hero ========== */
.hero {
  padding: calc(var(--header-h) + 48px) 16px 56px;
  text-align: center;
  background: linear-gradient(180deg, var(--color-bg-alt) 0%, var(--color-bg) 100%);
}

.hero-inner {
  max-width: var(--container);
  margin: 0 auto;
}

.hero-title {
  font-size: clamp(24px, 6vw, 32px);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 12px;
  line-height: 1.3;
}

.hero-desc {
  font-size: clamp(14px, 3.5vw, 16px);
  color: var(--color-text-muted);
  margin-bottom: 28px;
  max-width: 520px;
  margin-left: auto;
  margin-right: auto;
}

/* ========== 通用区块 ========== */
.section {
  padding: 48px 16px 56px;
}

.container {
  max-width: var(--container);
  margin: 0 auto;
}

.section-title {
  font-size: clamp(20px, 4vw, 24px);
  font-weight: 700;
  color: var(--color-text);
  text-align: center;
  margin-bottom: 8px;
}

.section-desc {
  font-size: 15px;
  color: var(--color-text-muted);
  text-align: center;
  margin-bottom: 32px;
  max-width: 480px;
  margin-left: auto;
  margin-right: auto;
}

/* ========== 服务列表 ========== */
.services {
  background: var(--color-bg-alt);
}

.service-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.service-item {
  padding: 24px;
  background: var(--color-bg);
  border-radius: 12px;
  border: 1px solid rgba(0,0,0,0.06);
  transition: box-shadow 0.2s, border-color 0.2s;
}

.service-item:hover {
  box-shadow: 0 4px 20px rgba(37, 99, 235, 0.08);
  border-color: rgba(37, 99, 235, 0.15);
}

.service-icon {
  display: inline-block;
  font-size: 28px;
  margin-bottom: 12px;
}

.service-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 8px;
}

.service-desc {
  font-size: 14px;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ========== 联系表单 ========== */
.cta {
  background: var(--color-bg);
}

.contact-form {
  max-width: 420px;
  margin: 0 auto;
}

.form-row {
  margin-bottom: 16px;
}

.form-input {
  width: 100%;
  padding: 12px 16px;
  font-size: 15px;
  font-family: inherit;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  background: var(--color-bg-alt);
  color: var(--color-text);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.form-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.form-input::placeholder {
  color: #94a3b8;
}

.form-textarea {
  resize: vertical;
  min-height: 88px;
}

.contact-form .btn {
  margin-top: 8px;
}

/* ========== 页脚 ========== */
.footer {
  padding: 24px 16px;
  background: var(--color-text);
  color: rgba(255,255,255,0.85);
  text-align: center;
}

.footer-copy {
  font-size: 13px;
  max-width: var(--container);
  margin: 0 auto;
}

.footer-icp {
  color: rgba(255,255,255,0.85);
  margin-top: 8px;
  display: inline-block;
}

.footer-icp:hover {
  color: #fff;
  text-decoration: underline;
}

/* ========== 手机端：导航折叠 ========== */
@media (max-width: 640px) {
  .nav-toggle {
    display: block;
  }

  .nav {
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    background: var(--color-bg-alt);
    flex-direction: column;
    padding: 16px;
    gap: 0;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: transform 0.2s, opacity 0.2s, visibility 0.2s;
  }

  .nav.is-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav a {
    display: block;
    padding: 14px 0;
    border-bottom: 1px solid #f1f5f9;
  }

  .nav a:last-child {
    border-bottom: none;
  }
}