/* Shared motion primitives. Loaded on every front-facing page from layout.html.
   Durations and easings come from the tokens in style.css. */

/* ---------------------------------------------------------------- anchors */

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--navbar);
}

/* --------------------------------------------------- scroll reveal (.js gated,
   so nothing is ever stuck invisible when JS is unavailable) */

.js .reveal {
    opacity: 0;
    transform: translateY(12px);
    transition: opacity var(--dur-slow) var(--ease-out),
                transform var(--dur-slow) var(--ease-out);
    transition-delay: calc(var(--reveal-i, 0) * 60ms);
    will-change: opacity, transform;
}

.js .reveal.is-visible {
    opacity: 1;
    transform: none;
    will-change: auto;
}

/* Reusable entrance, for elements that flip display and so can't transition. */
@keyframes fade-up {
    from {
        opacity: 0;
        transform: translateY(8px);
    }
}

/* --------------------------------------------- fade swap for AJAX rebuilds */

.fade-swap {
    transition: opacity var(--dur-base) var(--ease-standard);
}

.fade-swap.is-swapping {
    opacity: 0;
}

/* ------------------------------------------------------- focus affordance */

a,
button,
.trigger,
.form-control,
.form-select {
    transition: outline-color var(--dur-fast) var(--ease-standard),
                box-shadow var(--dur-fast) var(--ease-standard),
                color var(--dur-fast) var(--ease-standard),
                background-color var(--dur-fast) var(--ease-standard),
                border-color var(--dur-fast) var(--ease-standard);
}

/* Bootstrap sets its own transitions on .btn / .form-control; don't fight them. */
.btn,
.page-link {
    transition: color var(--dur-fast) var(--ease-standard),
                background-color var(--dur-fast) var(--ease-standard),
                border-color var(--dur-fast) var(--ease-standard),
                box-shadow var(--dur-fast) var(--ease-standard);
}

/* ------------------------------------------------------ cross-page fades */

@view-transition {
    navigation: auto;
}

@keyframes vt-fade-out {
    to { opacity: 0; }
}

@keyframes vt-fade-in {
    from { opacity: 0; }
}

::view-transition-old(root) {
    animation: vt-fade-out 90ms var(--ease-standard) both;
}

::view-transition-new(root) {
    animation: vt-fade-in 180ms var(--ease-out) both;
}

/* Opacity only, no transform: the navbar and footer are identical either side of
   a navigation, so they cross-fade against themselves invisibly and need no
   view-transition-name of their own. */

/* ------------------------------------------------------- reduced motion */

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        transition-delay: 0ms !important;
        scroll-behavior: auto !important;
    }

    @view-transition {
        navigation: none;
    }
}