.series-nav {
  margin: 34px 0 10px;
  padding: 18px 20px;
  border: 1px solid #e6e8eb;
  border-radius: 14px;
  background: #fff;
  box-shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 6px 20px rgba(16, 24, 40, 0.05);
  font-family: "Open Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

.series-nav-head {
  display: flex;
  align-items: center;
  gap: 12px;
}

.series-nav-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 9px;
  background: rgba(0, 138, 255, 0.1);
  color: #008aff;
  flex-shrink: 0;
}

.series-nav-heading {
  display: flex;
  flex-direction: column;
  line-height: 1.25;
  min-width: 0;
}

.series-nav-eyebrow {
  font-size: 0.67rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #008aff;
}

.series-nav-title {
  font-weight: 700;
  color: #1a2330;
  font-size: 1rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.series-nav-count {
  margin-left: auto;
  font-size: 0.85rem;
  color: #1a2330;
  font-weight: 700;
  white-space: nowrap;
}

.series-nav-count-total {
  color: #9aa6b6;
  font-weight: 600;
}

.series-nav-progress {
  margin-top: 13px;
  height: 5px;
  border-radius: 999px;
  background: #eef0f2;
  overflow: hidden;
}

.series-nav-progress-fill {
  display: block;
  height: 100%;
  border-radius: 999px;
  background: linear-gradient(90deg, #008aff, #58b0ff);
  transition: width 0.4s ease;
}

.series-nav-list {
  margin: 15px 0 2px;
}

.series-nav-list summary {
  cursor: pointer;
  font-size: 0.84rem;
  color: #008aff;
  font-weight: 600;
  list-style: none;
  user-select: none;
  outline: none;
}

.series-nav-list summary::-webkit-details-marker {
  display: none;
}

.series-nav-list summary::before {
  content: "▸";
  display: inline-block;
  margin-right: 5px;
  transition: transform 0.15s ease;
}

.series-nav-list[open] summary::before {
  transform: rotate(90deg);
}

.series-nav-list ol {
  margin: 12px 0 2px;
  padding-left: 22px;
}

.series-nav-list li {
  margin: 5px 0;
  font-size: 0.89rem;
  color: #4a5568;
}

.series-nav-list li a {
  color: #4a5568;
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

.series-nav-list li a:hover {
  color: #008aff;
  border-bottom-color: #008aff;
}

.series-nav-list li.is-current {
  font-weight: 700;
  color: #008aff;
  list-style-type: disc;
}

.series-nav-move {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 16px;
}

.series-nav-move > a,
.series-nav-move > span {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 12px 15px;
  border-radius: 10px;
  background: #fafbfc;
  border: 1px solid #eef0f2;
  text-decoration: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, transform 0.15s ease, background 0.15s ease;
}

.series-nav-move > a:hover {
  background: #fff;
  border-color: #cfe3ff;
  box-shadow: 0 4px 14px rgba(0, 138, 255, 0.1);
  transform: translateY(-1px);
}

.series-nav-next {
  text-align: right;
}

.series-nav-dir {
  font-size: 0.72rem;
  font-weight: 700;
  color: #008aff;
  text-transform: uppercase;
  letter-spacing: 0.4px;
}

.series-nav-name {
  font-size: 0.85rem;
  color: #3a4759;
  line-height: 1.4;
}

.series-nav-move > .is-disabled {
  opacity: 0.55;
  cursor: default;
}

.series-nav-move > .is-disabled .series-nav-dir {
  color: #9aa6b6;
}

body.dark-mode .series-nav {
  background: #1b1f27;
  border-color: #2b313c;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 6px 20px rgba(0, 0, 0, 0.25);
}

body.dark-mode .series-nav-icon {
  background: rgba(0, 138, 255, 0.16);
}

body.dark-mode .series-nav-title,
body.dark-mode .series-nav-count {
  color: #e8eaed;
}

body.dark-mode .series-nav-progress {
  background: #2b313c;
}

body.dark-mode .series-nav-list li,
body.dark-mode .series-nav-list li a {
  color: #aab3c0;
}

body.dark-mode .series-nav-move > a,
body.dark-mode .series-nav-move > span {
  background: #171b22;
  border-color: #2b313c;
}

body.dark-mode .series-nav-move > a:hover {
  background: #1f242d;
  border-color: #2f5075;
}

body.dark-mode .series-nav-name {
  color: #c2cad5;
}

@media (max-width: 575px) {
  .series-nav-move {
    grid-template-columns: 1fr;
  }
  .series-nav-next {
    text-align: left;
  }
}