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

body {
  font-family: "Microsoft YaHei", "PingFang SC", sans-serif;
  background: linear-gradient(135deg, #f5f7fa 0%, #e4e8ec 100%);
  min-height: 100vh;
  color: #333;
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 20px;
}

/* 头部导航 */
header {
  background: linear-gradient(135deg, #2563eb 0%, #3b82f6 100%);
  padding: 20px 0;
  box-shadow: 0 4px 20px rgba(37, 99, 235, 0.3);
  position: sticky;
  top: 0;
  z-index: 100;
}

header .container {
  padding: 0 20px;
}

.nav-wrapper {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 15px;
}

.logo {
  font-size: 28px;
  font-weight: bold;
  color: #fff;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

.nav-tabs {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.nav-tab {
  padding: 10px 20px;
  background: rgba(255,255,255,0.15);
  color: #fff;
  text-decoration: none;
  border-radius: 25px;
  font-size: 15px;
  transition: all 0.3s ease;
  border: 2px solid transparent;
}

.nav-tab:hover,
.nav-tab.active {
  background: #fff;
  color: #2563eb;
  border-color: #fff;
}

/* 页面标题 */
.page-title {
  text-align: center;
  font-size: 32px;
  color: #2563eb;
  margin: 30px 0;
  position: relative;
}

.page-title::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  width: 80px;
  height: 4px;
  background: linear-gradient(90deg, #2563eb, #3b82f6);
  border-radius: 2px;
}

/* 字母网格 */
.letter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
  gap: 20px;
  padding: 20px 0;
}

.letter-card {
  background: #fff;
  border-radius: 16px;
  padding: 15px;
  text-align: center;
  box-shadow: 0 4px 15px rgba(0,0,0,0.08);
  transition: all 0.3s ease;
  cursor: pointer;
  border: 2px solid transparent;
}

.letter-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(37, 99, 235, 0.2);
  border-color: #3b82f6;
}

.letter-card img {
  width: 80px;
  height: 80px;
  object-fit: contain;
  margin-bottom: 10px;
}

.letter-card .letter-num {
  font-size: 14px;
  color: #666;
  background: #f0f4ff;
  padding: 4px 12px;
  border-radius: 12px;
  display: inline-block;
}

/* 字母详情弹窗 */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.6);
  z-index: 1000;
  justify-content: center;
  align-items: center;
  backdrop-filter: blur(5px);
}

.modal.show {
  display: flex;
}

.modal-content {
  background: #fff;
  border-radius: 24px;
  padding: 40px;
  max-width: 400px;
  width: 90%;
  text-align: center;
  position: relative;
  animation: modalIn 0.3s ease;
}

@keyframes modalIn {
  from {
    opacity: 0;
    transform: scale(0.9);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.modal-close {
  position: absolute;
  top: 15px;
  right: 20px;
  font-size: 28px;
  color: #999;
  cursor: pointer;
  transition: color 0.3s;
}

.modal-close:hover {
  color: #2563eb;
}

.modal-content img {
  width: 150px;
  height: 150px;
  object-fit: contain;
  margin-bottom: 20px;
}

.modal-content h3 {
  font-size: 24px;
  color: #2563eb;
  margin-bottom: 10px;
}

.modal-content p {
  color: #666;
  font-size: 16px;
}

/* 页脚 */
footer {
  text-align: center;
  padding: 30px 0;
  color: #888;
  font-size: 14px;
}

/* 响应式 */
@media (max-width: 600px) {
  .container {
    padding: 15px;
  }

  .page-title {
    font-size: 24px;
  }

  .letter-grid {
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 12px;
  }

  .letter-card img {
    width: 60px;
    height: 60px;
  }

  .nav-tab {
    padding: 8px 14px;
    font-size: 13px;
  }

  .logo {
    font-size: 22px;
  }
}

/* 手机端适配 */
@media (max-width: 480px) {
  header {
    padding: 12px 0;
  }

  .nav-wrapper {
    flex-direction: column;
    gap: 10px;
  }

  .logo {
    font-size: 20px;
  }

  .nav-tabs {
    gap: 4px;
  }

  .nav-tab {
    padding: 6px 10px;
    font-size: 12px;
    border-radius: 15px;
  }

  .page-title {
    font-size: 22px;
  }

  .letter-grid {
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: 10px;
  }

  .letter-card {
    padding: 10px;
  }

  .letter-card img {
    width: 50px;
    height: 50px;
  }

  .letter-card .letter-num {
    font-size: 11px;
    padding: 2px 8px;
  }

  .word-list {
    grid-template-columns: 1fr;
  }

  .word-card {
    padding: 14px;
  }

  .word-letters img {
    width: 28px;
    height: 28px;
  }

  .word-chinese {
    font-size: 16px;
  }

  .phrase-list {
    grid-template-columns: 1fr;
  }

  .phrase-card {
    padding: 15px;
  }

  .phrase-letters img {
    width: 32px;
    height: 32px;
  }

  .modal-content {
    padding: 25px 20px;
    margin: 15px;
  }

  .modal-content img {
    width: 100px;
    height: 100px;
  }

  .syntax-image img {
    max-width: 100%;
  }
}