/* style.css */
:root {
  --font-color: #333;
  --bg-color: #fff;
  --primary: #000;
  --secondary: #f5f5f5;
  --border-color: #e0e0e0;
  --spacing-unit: 1rem;
}

* {
  box-sizing: border-box;
}

body {
  font-family: "Helvetica", "Arial", "思源黑体", "苹方", sans-serif;
  color: var(--font-color);
  margin: 0;
  padding: 0;
  background-color: var(--bg-color);
  line-height: 1.6;
}

/* 固定导航栏 */
nav {
  background-color: var(--bg-color);
  padding: 0 var(--spacing-unit);
  position: fixed;
  width: 100%;
  top: 0;
  z-index: 1000;
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

nav ul {
  display: flex;
  justify-content: center;
  align-items: center;
  list-style: none;
  padding: 0;
  margin: 0;
}

nav li {
  margin: 0;
}

nav a {
  display: block;
  padding: calc(var(--spacing-unit) * 1.5) calc(var(--spacing-unit) * 2);
  text-decoration: none;
  color: var(--font-color);
  font-weight: 400;
  letter-spacing: 0.05em;
  transition: all 0.3s ease;
  position: relative;
}

nav a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  width: 0;
  height: 1px;
  background-color: var(--primary);
  transform: translateX(-50%);
  transition: width 0.3s ease;
}

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

nav a:hover::after,
nav a:focus::after {
  width: 80%;
}

nav a.active {
  font-weight: 500;
}

/* Hero Section */
#hero {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  background-color: var(--secondary);
}

#hero img {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  z-index: 1;
}

#hero .content {
  position: relative;
  z-index: 2;
  text-align: center;
  color: #fff;
  padding: var(--spacing-unit);
  background-color: rgba(0, 0, 0, 0.4);
}

#hero .content h1 {
  margin: 0;
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 300;
  letter-spacing: 0.1em;
}

/* Main Content */
main {
  margin-top: 80px;
  min-height: calc(100vh - 80px);
}

section {
  padding: calc(var(--spacing-unit) * 5) 0;
}

.grid {
  display: grid;
  gap: var(--spacing-unit);
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.grid-item {
  background-color: var(--secondary);
  overflow: hidden;
  transition: transform 0.3s ease;
}

.grid-item:hover {
  transform: translateY(-5px);
}

.grid-item img {
  width: 100%;
  height: auto;
  display: block;
  transition: opacity 0.3s ease;
}

.grid-item:hover img {
  opacity: 0.85;
}

.grid-item .caption {
  padding: var(--spacing-unit);
  text-align: center;
  font-size: 0.9rem;
  letter-spacing: 0.05em;
}

/* Footer */
footer {
  text-align: center;
  padding: var(--spacing-unit);
  background-color: var(--bg-color);
  border-top: 1px solid var(--border-color);
  font-size: 0.9rem;
  color: #777;
}

/* Utility Classes */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-unit);
}

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

/* Responsive */
@media (max-width: 768px) {
  nav a {
    padding: var(--spacing-unit) calc(var(--spacing-unit) * 1.2);
    font-size: 0.9rem;
  }
  
  .container {
    padding: 0 calc(var(--spacing-unit) * 0.5);
  }
}