/* 全局变量定义 */
:root {
  --color-primary: #1e3a8a;
  --color-secondary: #06b6d4;
  --color-accent: #0ea5e9;
  --color-dark: #0f172a;
  --color-light: #f8fafc;
  --color-gray: #64748b;
  --transition-base: all 0.3s ease;
}

/* 全局重置与基础样式 */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  line-height: 1.6;
  color: var(--color-dark);
  background: var(--color-light);
  overflow-x: hidden;
}

/* 平滑滚动 */
html {
  scroll-behavior: smooth;
}

/* 图片优化 */
img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* 链接样式 */
a {
  text-decoration: none;
  color: inherit;
  transition: var(--transition-base);
}

/* 按钮基础样式 */
button {
  cursor: pointer;
  border: none;
  outline: none;
  transition: var(--transition-base);
}

/* 容器最大宽度 */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 1rem;
}

/* 响应式断点 */
@media (min-width: 640px) {
  .container {
    padding: 0 2rem;
  }
}

@media (min-width: 1024px) {
  .container {
    padding: 0 3rem;
  }
}

/* 卡片悬停效果 */
.card-hover {
  transition: var(--transition-base);
}

.card-hover:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 40px rgba(6, 182, 212, 0.15);
}

/* 渐变背景 */
.gradient-bg {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
}

/* 文字渐变 */
.gradient-text {
  background: linear-gradient(135deg, var(--color-secondary), var(--color-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* 加载动画 */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in-up {
  animation: fadeInUp 0.8s ease-out forwards;
}

/* 导航栏激活状态 */
.nav-active {
  color: var(--color-secondary);
  position: relative;
}

.nav-active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--color-secondary);
}

/* 响应式网格 */
.grid-responsive {
  display: grid;
  gap: 2rem;
  grid-template-columns: 1fr;
}

@media (min-width: 768px) {
  .grid-responsive {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .grid-responsive {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* 服务卡片网格 */
.service-grid {
  display: grid;
  gap: 2rem;
  grid-template-columns: 1fr;
}

@media (min-width: 768px) {
  .service-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* 图片覆盖层效果 */
.img-overlay {
  position: relative;
  overflow: hidden;
}

.img-overlay::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(180deg, transparent 0%, rgba(15, 23, 42, 0.3) 100%);
  transition: var(--transition-base);
}

.img-overlay:hover::after {
  background: linear-gradient(180deg, transparent 0%, rgba(6, 182, 212, 0.2) 100%);
}

/* 分隔线 */
.divider {
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--color-secondary), var(--color-accent));
  margin: 1rem 0;
  border-radius: 2px;
}

/* 无障碍优化 */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* 焦点可见性 */
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--color-secondary);
  outline-offset: 2px;
}