/* ============================================
   年级卡片 - 导航组件
   ============================================ */

.grade-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-lg);
}

.grade-card {
  position: relative;
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  padding: var(--space-xl);
  background: var(--bg-white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-light);
  transition: all var(--transition);
  overflow: hidden;
}

/* 卡片背景装饰 */
.grade-card-bg {
  position: absolute;
  inset: 0;
  opacity: 0;
  transition: opacity var(--transition);
  border-radius: inherit;
}

.grade-card[data-grade="1"] .grade-card-bg { background: linear-gradient(135deg, #FFF0F0 0%, #FFE0E0 100%); }
.grade-card[data-grade="2"] .grade-card-bg { background: linear-gradient(135deg, #FFF8ED 0%, #FFEDCC 100%); }
.grade-card[data-grade="3"] .grade-card-bg { background: linear-gradient(135deg, #FFFCED 0%, #FFF5CC 100%); }
.grade-card[data-grade="4"] .grade-card-bg { background: linear-gradient(135deg, #EDFFF0 0%, #D6FFE0 100%); }
.grade-card[data-grade="5"] .grade-card-bg { background: linear-gradient(135deg, #EDF5FF 0%, #CCDFFF 100%); }
.grade-card[data-grade="6"] .grade-card-bg { background: linear-gradient(135deg, #F3EDFF 0%, #E0CCFF 100%); }

.grade-card:hover .grade-card-bg {
  opacity: 1;
}

.grade-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
}

/* 年级图标 */
.grade-card-icon {
  position: relative;
  z-index: 1;
  width: 64px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  border-radius: var(--radius-md);
  background: var(--bg-light);
  flex-shrink: 0;
  transition: all var(--transition);
}

.grade-card[data-grade="1"]:hover .grade-card-icon { background: var(--grade-1); }
.grade-card[data-grade="2"]:hover .grade-card-icon { background: var(--grade-2); }
.grade-card[data-grade="3"]:hover .grade-card-icon { background: var(--grade-3); }
.grade-card[data-grade="4"]:hover .grade-card-icon { background: var(--grade-4); }
.grade-card[data-grade="5"]:hover .grade-card-icon { background: var(--grade-5); }
.grade-card[data-grade="6"]:hover .grade-card-icon { background: var(--grade-6); }

/* 卡片信息 */
.grade-card-info {
  position: relative;
  z-index: 1;
  flex: 1;
}

.grade-card-info h3 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
}

.grade-card-info p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.5;
  margin-bottom: var(--space-sm);
}

.grade-card-units {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--primary);
  background: var(--primary-bg);
  padding: 2px 10px;
  border-radius: var(--radius-full);
}

/* 箭头 */
.grade-card-arrow {
  position: relative;
  z-index: 1;
  font-size: 1.5rem;
  color: var(--text-light);
  transition: all var(--transition);
  flex-shrink: 0;
}

.grade-card:hover .grade-card-arrow {
  color: var(--primary);
  transform: translateX(4px);
}

/* 响应式 */
@media (max-width: 768px) {
  .grade-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .grade-card {
    padding: var(--space-md);
    gap: var(--space-md);
  }

  .grade-card-icon {
    width: 48px;
    height: 48px;
    font-size: 1.5rem;
  }

  .grade-card-info h3 {
    font-size: 1.2rem;
  }
}