/* 1. 变量 & 基础 */
:root {
  --primary: #6366f1;
  --secondary: #70b6f8;
  --bg: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --card-bg: rgba(227, 226, 226, 0.7);
  --radius: 16px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
  --transition: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  margin: 0;
  height: 100vh;
  background: url("images/background.png") no-repeat center/cover fixed;
  font-family: "Inter", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: #222;
  line-height: 1.6;
}

header {
  padding: 2rem 1rem 1rem;
  text-align: center;
  background: transparent;   /* 无背景 */
  box-shadow: none;        
  position: static;       
}
header h1 {
  font-size: 2.2rem;
  font-weight: 700;
  letter-spacing: 1px;
  background: black;
  -webkit-background-clip: text;
          background-clip: text;
  -webkit-text-fill-color: transparent;
          color: transparent;
}

/* 3. 卡片容器：固定 3 列 */
.card-container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  max-width: 1300px;
  margin: 3rem auto;
  padding: 0 1rem;
}

/* 4. 卡片 */
.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  cursor: pointer;
  transition: var(--transition);
  position: relative;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.2);
}

.card:hover::after {
  left: 150%;
}

.card img {
  width: 100%;
  height: 260px;
  object-fit: cover;
  display: block;
}
.card h2 {
  font-size: 1.4rem;
  margin: 1rem 1rem 0.5rem;
  font-weight: 600;
  text-align: center;
}
.card p {
  font-size: 0.95rem;
  color: #444;
  margin: 0 1rem 1.5rem;
  text-align: center;
}

/* 5. 按钮式页脚 */
footer {
  text-align: center;
  padding: 2.5rem 1rem;
}

footer .copyright {
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.8);
}

/* 6. 响应式 */
@media (max-width: 900px) {
  .card-container {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 600px) {
  .card-container {
    grid-template-columns: 1fr;
  }
}