Glass tooltip

/* HTML:
<button class="gt-trigger">
  Share
  <span class="gt-tip" role="tooltip">Copy link to clipboard</span>
</button> */

.gt-trigger {
  position: relative;
  display: inline-flex;
  align-items: center;
  cursor: pointer;
}

.gt-tip {
  position: absolute;
  bottom: calc(100% + 0.625rem);
  left: 50%;
  transform: translateX(-50%) translateY(4px);
  white-space: nowrap;
  padding: 0.45rem 0.85rem;
  border-radius: 0.5rem;
  font-size: 0.78rem;
  font-weight: 500;
  color: oklch(0.93 0.01 260);

  /* Frosted glass */
  background: oklch(0.22 0.03 260 / 0.65);
  backdrop-filter: blur(12px) saturate(1.4);
  -webkit-backdrop-filter: blur(12px) saturate(1.4);
  border: 1px solid oklch(0.40 0.04 260 / 0.5);
  box-shadow: 0 4px 16px oklch(0 0 0 / 0.35);

  pointer-events: none;
  opacity: 0;
  transition: opacity 0.18s ease, transform 0.18s ease;
  z-index: 10;
}

/* Arrow caret */
.gt-tip::after {
  content: '';
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%);
  border: 5px solid transparent;
  border-top-color: oklch(0.40 0.04 260 / 0.5);
}

.gt-trigger:hover .gt-tip,
.gt-trigger:focus-visible .gt-tip {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

@media (prefers-reduced-motion: reduce) {
  .gt-tip {
    transition: opacity 0.18s ease;
    transform: translateX(-50%) translateY(0);
  }
}

You are a senior frontend engineer building polished UI micro-interactions.

Goal: A CSS-only frosted glass tooltip that appears above a trigger element on hover and focus-visible. Uses backdrop-filter: blur for the glass effect, oklch() semi-transparent background, and a smooth fade + slide-up entrance transition.

Technical constraints:
- Position the tooltip absolutely above the trigger using bottom: calc(100% + 0.625rem) and left: 50% with transform: translateX(-50%).
- Frosted glass: background with an oklch() color at ~0.65 alpha, backdrop-filter: blur(12px) saturate(1.4), plus -webkit-backdrop-filter for Safari.
- Include a border with a semi-transparent oklch() color and a box-shadow for depth.
- Entrance: start at opacity: 0 and translateY(4px), transition to opacity: 1 and translateY(0) on hover/focus-visible.
- Add a CSS border triangle caret using ::after with border tricks pointing downward from the tooltip bottom.
- Use pointer-events: none on the tooltip so it cannot be accidentally hovered as a separate element.
- Wrap transform transition in @media (prefers-reduced-motion: reduce) — keep opacity transition, remove translateY movement.

Framework variant (pick one):
A) Vanilla HTML + CSS — tooltip span is a child of the trigger button.
B) React component — accepts label and children props; renders the tooltip via a portal to avoid overflow: hidden clipping on ancestor elements.

Edge cases to handle:
- Viewport edges: tooltip near the left or right edge should shift horizontally via clamp() or JS repositioning to stay on screen.
- backdrop-filter unsupported: fallback to a solid dark background that still looks intentional.
- Long tooltip text: add max-width and white-space: normal to prevent overflow on small screens.
- Touch devices: tooltip should also appear on :focus-visible triggered by tap, not just pointer hover.

Return HTML + CSS.