.subject-nav {
  margin-bottom: 15px;
}
.subject-btn {
  margin-right: 8px;
  padding: 6px 12px;
  border-radius: 6px;
  border: 1px solid #ccc;
  background: #f0f0f0;
  cursor: pointer;
}
.subject-btn.active {
  background: #0073aa;
  color: #fff;
}
.question-wrap {
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 6px;
}