body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  margin: 0;
  padding: 20px;
  background-color: #f0f2f5;
  color: #333;
}
h1, #accordion-container {
  max-width: 800px;
  margin: 0 auto;
}
h1 {
  text-align: center;
  color: #4a5568;
  margin-bottom: 30px;
}
.accordion-list {
  list-style: none;
  padding: 0;
}
.accordion-list .accordion-list {
  padding-top: 10px;
  padding-left: 15px;
}
details {
  margin-bottom: 12px;
  background-color: #fff;
  border-radius: 12px;
  box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}
details details {
  box-shadow: none;
  border: 1px solid #eee;
}
summary {
  display: block;
  padding: 16px 20px 16px 40px;
  cursor: pointer;
  position: relative;
  font-weight: 600;
  color: #2d3748;
  user-select: none;
  outline: none;
  border-radius: 12px;
  transition: background 0.2s;
}
summary::-webkit-details-marker { display: none; }
summary::before {
  content: '+';
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  width: 20px;
  height: 20px;
  background-color: #e2e8f0;
  color: #718096;
  border-radius: 50%;
  text-align: center;
  line-height: 20px;
  font-size: 14px;
  font-weight: bold;
}
details[open] > summary {
  background-color: #f7fafc;
  border-bottom-left-radius: 0;
  border-bottom-right-radius: 0;
  color: #3182ce;
}
details[open] > summary::before {
  content: '-';
  background-color: #3182ce;
  color: #fff;
}
.hint-content {
  padding: 20px;
  line-height: 1.6;
  color: #4a5568;
  border-top: 1px solid #f0f0f0;
}
.hint-content img {
  max-width: 100%;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}