Segmented Control

<div class="nuda-seg" role="tablist" aria-label="View">
  <div class="nuda-seg__indicator" aria-hidden="true"></div>
  <button type="button" class="nuda-seg__btn nuda-seg__btn--active" role="tab" aria-selected="true">Day</button>
  <button type="button" class="nuda-seg__btn" role="tab" aria-selected="false">Week</button>
  <button type="button" class="nuda-seg__btn" role="tab" aria-selected="false">Month</button>
</div>

/* Segmented Control
   Pill-style switch with a sliding indicator.
   Customize: --seg-bg, --seg-pill */

.nuda-seg {
  --seg-bg: rgba(255, 255, 255, 0.06);
  --seg-pill: #111114;
  position: relative;
  display: flex;
  width: 260px;
  padding: 3px;
  background: var(--seg-bg);
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: 10px;
  font-family: system-ui;
}

.nuda-seg__indicator {
  position: absolute;
  top: 3px;
  bottom: 3px;
  left: 3px;
  width: calc((100% - 6px) / 3);
  background: var(--seg-pill);
  border-radius: 8px;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.4);
  animation: nuda-seg-slide 4s cubic-bezier(0.5, 1.4, 0.5, 1) infinite;
  will-change: transform;
}

.nuda-seg__btn {
  position: relative;
  z-index: 1;
  flex: 1;
  appearance: none;
  background: transparent;
  border: 0;
  color: #a0a0a8;
  font: 600 12px/1 system-ui;
  min-height: 32px;
  cursor: pointer;
  transition: color 0.25s;
}

.nuda-seg__btn--active { color: #fafafa; }

@keyframes nuda-seg-slide {
  0%, 25% { transform: translateX(0); }
  33%, 58% { transform: translateX(100%); }
  66%, 91% { transform: translateX(200%); }
  100% { transform: translateX(0); }
}

@media (prefers-reduced-motion: reduce) {
  .nuda-seg__indicator { animation: none; }
}