/* ===== Page ===== */
* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: #f5f6f8;
  color: #1a1a1a;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 17px;
  line-height: 1.65;
}

.document {
  max-width: 760px;
  margin: 48px auto;
  padding: 40px 48px;
  background: #ffffff;
  border-radius: 12px;
  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.06);
}

/* ===== Sections ===== */
.section {
  border-bottom: 1px solid #eaecef;
}
.section:last-child {
  border-bottom: none;
}

/* Header button — full-width, transparent, shows title + arrow */
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  width: 100%;
  padding: 18px 0;
  background: transparent;
  border: none;
  cursor: pointer;
  text-align: left;
  color: inherit;
  font: inherit;
  transition: opacity 0.15s ease;
}
.section-header:hover {
  opacity: 0.75;
}
.section-header:focus-visible {
  outline: 2px solid #4a90e2;
  outline-offset: 4px;
  border-radius: 4px;
}

.section-header-static {
  padding: 24px 0 8px;
  cursor: default;
}

/* Titles */
.section-title {
  margin: 0;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.section-h1 .section-title {
  font-size: 2em;
  line-height: 1.25;
}
.section-h2 .section-title {
  font-size: 1.5em;
  line-height: 1.3;
}
.section-h3 .section-title {
  font-size: 1.2em;
  line-height: 1.35;
  color: #333;
}

/* Indent sub-sections slightly */
.section-h3 {
  padding-left: 16px;
  border-left: 2px solid #eaecef;
  margin-left: 4px;
}

/* ===== Arrow toggle ===== */
.arrow {
  flex-shrink: 0;
  display: inline-block;
  font-size: 0.85em;
  color: #666;
  transition: transform 0.25s ease;
  user-select: none;
}
.section-header[aria-expanded="true"] .arrow {
  transform: rotate(180deg);
}

/* ===== Body content ===== */
.section-body {
  padding: 4px 0 20px;
  animation: fadeIn 0.25s ease;
}

.section-body p {
  margin: 0 0 14px;
}
.section-body p:last-child {
  margin-bottom: 0;
}

.section-body ul {
  margin: 0 0 14px;
  padding-left: 22px;
}
.section-body li {
  margin-bottom: 6px;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .document {
    margin: 0;
    padding: 24px 20px;
    border-radius: 0;
    box-shadow: none;
  }
  .section-h1 .section-title { font-size: 1.55em; }
  .section-h2 .section-title { font-size: 1.25em; }
  .section-h3 .section-title { font-size: 1.08em; }
  body { font-size: 16px; }
}