/* ─── Back-to-top ──────────────────────────────────────────────────────
   Site chrome (ships fleet-wide from parts/footer.html — deliberately not
   opt-in; [hzo_back_to_top] can emit further instances). back-to-top.js
   (Phase-2 widget; behavior moved out of main.js) adds .is-visible once
   scrollY passes two viewports — or the data-hzo-back-to-top-threshold[-px]
   override; click smooth-scrolls to top (instant under reduced motion).
   Quiet circle: brand bg, white arrow, --shadow-md, 44px target. Rides
   between --z-sticky-bar (10) and --z-header (20) — above the mobile sticky
   CTA, below every overlay. Hidden from print (components/_base/
   print-styles.css). */
.hzo-back-to-top {
    position: fixed;
    right: var(--space-lg);
    bottom: calc(var(--space-lg) + env(safe-area-inset-bottom, 0px));
    z-index: var(--z-back-to-top, 15);
    width: 44px;
    height: 44px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 0;
    border-radius: var(--radius-full);
    background: var(--back-to-top-bg, var(--brand));
    color: var(--back-to-top-color, var(--text-on-brand));
    box-shadow: var(--shadow-md);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(var(--space-sm));
    transition: opacity var(--duration-base) var(--ease-standard),
                transform var(--duration-base) var(--ease-out),
                visibility var(--duration-base),
                background var(--duration-base) var(--ease-standard);
}
.hzo-back-to-top svg { width: 20px; height: 20px; display: block; }
.hzo-back-to-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: none;
}
.hzo-back-to-top:hover { background: var(--back-to-top-bg-hover, var(--brand-hover-on-light)); }
.hzo-back-to-top:focus-visible { outline: 2px solid var(--color-focus); outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) {
    .hzo-back-to-top { transition: none; transform: none; }
}