<label class="tg-dn" aria-label="Theme: light or dark">
  <input class="tg-dn-input" type="checkbox" checked>
  <span class="tg-dn-track" aria-hidden="true">
    <span class="tg-dn-thumb">
      <span class="tg-dn-crater tg-dn-c1"></span>
      <span class="tg-dn-crater tg-dn-c2"></span>
      <span class="tg-dn-crater tg-dn-c3"></span>
    </span>
    <span class="tg-dn-star tg-dn-s1"></span>
    <span class="tg-dn-star tg-dn-s2"></span>
    <span class="tg-dn-star tg-dn-s3"></span>
  </span>
</label>

.tg-dn {
  display: inline-flex;
  cursor: pointer;
  user-select: none;
}
.tg-dn-input {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0);
  white-space: nowrap; border: 0;
}
.tg-dn-track {
  position: relative;
  width: 72px;
  height: 36px;
  background: linear-gradient(180deg, #87ceeb 0%, #4a90c2 100%);
  border-radius: 999px;
  overflow: hidden;
  transition: background 0.4s ease;
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.2);
}
.tg-dn-thumb {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 30px; height: 30px;
  border-radius: 50%;
  background: radial-gradient(circle at 35% 35%, #ffe066 0%, #f5a623 90%);
  box-shadow: 0 0 14px rgba(255, 224, 102, 0.7);
  transition: left 0.4s cubic-bezier(0.4, 0, 0.2, 1),
              background 0.4s ease,
              box-shadow 0.4s ease;
}
.tg-dn-crater {
  position: absolute;
  border-radius: 50%;
  background: #2a2a30;
  opacity: 0;
  transition: opacity 0.4s ease;
}
.tg-dn-c1 { top: 6px;  left: 8px;  width: 6px;  height: 6px; }
.tg-dn-c2 { top: 14px; left: 18px; width: 4px;  height: 4px; }
.tg-dn-c3 { top: 20px; left: 6px;  width: 5px;  height: 5px; }
.tg-dn-star {
  position: absolute;
  width: 2px; height: 2px;
  background: #fff;
  border-radius: 50%;
  opacity: 0;
  transition: opacity 0.4s ease;
}
.tg-dn-s1 { top: 8px;  left: 14px; }
.tg-dn-s2 { top: 18px; left: 24px; width: 1.5px; height: 1.5px; }
.tg-dn-s3 { top: 10px; left: 28px; }
.tg-dn-input:not(:checked) ~ .tg-dn-track {
  background: linear-gradient(180deg, #0a1322 0%, #1c2540 100%);
}
.tg-dn-input:not(:checked) ~ .tg-dn-track .tg-dn-thumb {
  left: 39px;
  background: radial-gradient(circle at 35% 35%, #e8e6f0 0%, #a8a5bb 90%);
  box-shadow: 0 0 12px rgba(168, 165, 187, 0.5);
}
.tg-dn-input:not(:checked) ~ .tg-dn-track .tg-dn-crater { opacity: 0.5; }
.tg-dn-input:not(:checked) ~ .tg-dn-track .tg-dn-star { opacity: 0.85; }
.tg-dn-input:focus-visible ~ .tg-dn-track {
  outline: 2px solid #ffe066;
  outline-offset: 3px;
}
@media (prefers-reduced-motion: reduce) {
  .tg-dn-track,
  .tg-dn-thumb,
  .tg-dn-crater,
  .tg-dn-star { transition: none; }
}