/* "Up" at the bottom centre of the screen. Ink follows the background
   (tone-watch.js). */

.page-top {
    position: fixed;
    inset-block-end: calc(max(8px, 0.9vw) + var(--page-top-lift, 0px));
    left: 50%;
    z-index: calc(var(--z-header) - 1);
    min-width: 44px;
    min-height: 44px;
    padding: 0 8px;
    background: none;
    border: 0;
    color: var(--chrome-ink-light);
    text-shadow: var(--chrome-shadow-dark);
    font-family: var(--font-serif);
    font-size: max(15px, 1.05vw);
    letter-spacing: 0.04em;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translate(-50%, 6px);
    transition:
        opacity var(--dur-slow) var(--ease-out),
        transform var(--dur-slow) var(--ease-out),
        visibility 0s linear var(--dur-slow),
        color var(--dur-base) var(--ease-out);
}

.page-top[data-bg="light"] {
    color: var(--chrome-ink-dark);
    text-shadow: none;
}

.page-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: translate(-50%, 0);
    transition-delay: 0s;
}

.page-top.is-visible:hover { opacity: 0.65; }

.page-top:focus-visible {
    outline: 1px solid currentColor;
    outline-offset: 2px;
}

body:has(.site-side__bar.is-open) .page-top {
    opacity: 0;
    visibility: hidden;
}