/* ============================================================
   Site header / primary navigation
   ============================================================ */

.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: saturate(180%) blur(12px);
    -webkit-backdrop-filter: saturate(180%) blur(12px);
    border-bottom: 1px solid transparent;
    transition: border-color 0.3s var(--ease), background 0.3s var(--ease);
}
.site-header[data-elevated="true"] {
    border-bottom-color: var(--paper-line);
    background: rgba(255, 255, 255, 0.96);
}

.site-header__inner {
    width: var(--container-w);
    margin-inline: auto;
    height: var(--header-h);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

/* Brand */
.site-header__brand {
    display: inline-flex;
    align-items: center;
    gap: 0.7rem;
    color: var(--ink);
    flex-shrink: 0;
    transition: opacity 0.25s;
}
.site-header__brand:hover { opacity: 0.7; }
.site-header__logo {
    width: 2.1rem;
    height: 2.1rem;
    flex-shrink: 0;
}
.site-header__brand-text {
    display: flex;
    flex-direction: column;
    line-height: 1;
    gap: 0.25rem;
}
.site-header__brand-mark {
    font-family: var(--font-display);
    font-weight: 500;
    font-size: clamp(0.95rem, 0.85rem + 0.3vw, 1.05rem);
    letter-spacing: 0.02em;
}
.site-header__brand-sub {
    font-family: var(--font-body);
    font-size: 0.72rem;
    font-weight: 300;
    color: var(--ink-muted);
    letter-spacing: 0.04em;
}

/* Toggle (mobile) */
.site-header__toggle {
    display: none;
    width: 2.4rem;
    height: 2.4rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--paper-rule);
    background: transparent;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 4px;
    transition: background 0.25s, border-color 0.25s;
}
.site-header__toggle span {
    display: block;
    width: 16px;
    height: 1.6px;
    background: var(--ink);
    border-radius: 2px;
    transition: transform 0.3s var(--ease), opacity 0.25s;
    transform-origin: center;
}
.site-header__toggle--open span:nth-child(1) { transform: translateY(5.6px) rotate(45deg); }
.site-header__toggle--open span:nth-child(2) { opacity: 0; }
.site-header__toggle--open span:nth-child(3) { transform: translateY(-5.6px) rotate(-45deg); }

/* Nav list */
.site-nav__list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    align-items: center;
    gap: clamp(1rem, 0.5rem + 1.4vw, 2rem);
}
.site-nav__link {
    font-family: var(--font-body);
    font-size: clamp(0.88rem, 0.8rem + 0.25vw, 0.98rem);
    font-weight: 400;
    color: var(--ink-soft);
    position: relative;
    padding: 0.4rem 0;
    transition: color 0.25s;
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
}
.site-nav__link::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -2px;
    height: 1.5px;
    background: var(--accent);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.3s var(--ease);
}
.site-nav__link:hover,
.site-nav__link[aria-current="page"] {
    color: var(--accent);
}
.site-nav__link:hover::after,
.site-nav__link[aria-current="page"]::after {
    transform: scaleX(1);
}

/* Caret */
.site-nav__caret {
    width: 0.5em;
    height: 0.5em;
    border-right: 1.4px solid currentColor;
    border-bottom: 1.4px solid currentColor;
    transform: translateY(-2px) rotate(45deg);
    transition: transform 0.25s var(--ease);
    margin-left: 0.1em;
}
.site-nav__item--has-children.is-open .site-nav__caret {
    transform: translateY(2px) rotate(-135deg);
}

/* Submenu (desktop hover, mobile click) */
.site-nav__item--has-children {
    position: relative;
}
.site-nav__submenu {
    position: absolute;
    top: 100%;
    left: -1rem;
    list-style: none;
    margin: 0;
    /* Top padding absorbs what used to be a 0.6rem `top` offset — keeps the
       visual gap, but the submenu element now touches the trigger so the
       hover state survives the mouse trip from link to submenu. */
    padding: 1.1rem 0.5rem 0.5rem;
    background: var(--paper);
    border: 1px solid var(--paper-line);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lift);
    min-width: 180px;
    opacity: 0;
    transform: translateY(-6px);
    pointer-events: none;
    transition: opacity 0.25s var(--ease), transform 0.25s var(--ease);
    z-index: 10;
}
/* Invisible bridge over any sub-pixel gap between the trigger and the panel,
   so the hover state is continuous even with rounded layout values. */
.site-nav__item--has-children::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    height: 0.6rem;
    pointer-events: none;
}
.site-nav__item--has-children:hover::after,
.site-nav__item--has-children:focus-within::after {
    pointer-events: auto;
}
.site-nav__item--has-children:hover .site-nav__submenu,
.site-nav__item--has-children:focus-within .site-nav__submenu,
.site-nav__item--has-children.is-open .site-nav__submenu {
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
}
.site-nav__submenu a {
    display: block;
    padding: 0.5rem 0.75rem;
    font-size: var(--t-small);
    color: var(--ink-soft);
    border-radius: var(--radius-sm);
    transition: background 0.2s, color 0.2s;
}
.site-nav__submenu a:hover {
    background: var(--paper-2);
    color: var(--accent);
}

/* Mobile breakpoint */
@media (max-width: 960px) {
    /* Drop backdrop-filter on mobile. Per spec, backdrop-filter creates a
       containing block for descendant `position: fixed` elements — which would
       force the mobile nav's `inset: 0` to resolve against the (tiny) header
       box instead of the viewport, hiding the close button and locking scroll. */
    .site-header {
        backdrop-filter: none;
        -webkit-backdrop-filter: none;
        background: rgba(255, 255, 255, 0.96);
    }

    .site-header__toggle {
        display: inline-flex;
        /* Stays above the open nav so the close (X) is always reachable. */
        position: relative;
        z-index: 110;
    }

    .site-nav {
        position: fixed;
        inset: 0;
        background: var(--paper);
        padding: calc(var(--header-h) + 2rem) var(--gutter) 2rem;
        opacity: 0;
        pointer-events: none;
        transform: translateY(-1rem);
        transition: opacity 0.3s var(--ease), transform 0.3s var(--ease);
        overflow-y: auto;
        z-index: 105;
    }
    .site-nav--open {
        opacity: 1;
        pointer-events: auto;
        transform: translateY(0);
    }
    .site-nav__list {
        flex-direction: column;
        align-items: stretch;
        gap: 0;
    }
    .site-nav__list > li {
        border-bottom: 1px solid var(--paper-line);
    }
    .site-nav__link {
        display: flex;
        justify-content: space-between;
        font-family: var(--font-body);
        font-size: clamp(1.2rem, 0.9rem + 1.6vw, 1.6rem);
        font-weight: 500;
        color: var(--ink);
        padding: 1rem 0;
        width: 100%;
    }
    .site-nav__link::after { display: none; }

    .site-nav__submenu {
        position: static;
        opacity: 1;
        pointer-events: auto;
        transform: none;
        background: transparent;
        border: 0;
        box-shadow: none;
        /* Padding is 0 while collapsed so the panel takes no vertical space.
           Restored when `is-open` so the items have breathing room. */
        padding: 0 0 0 0.5rem;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s var(--ease), padding 0.3s var(--ease);
    }
    .site-nav__item--has-children.is-open .site-nav__submenu {
        max-height: 320px;
        padding: 0.25rem 0 1rem 0.5rem;
    }
    /* The desktop hover-bridge pseudo-element is unnecessary on mobile and
       would steal taps under the dropdown row — disable it. */
    .site-nav__item--has-children::after { display: none; }
    .site-nav__submenu a {
        font-family: var(--font-body);
        font-size: var(--t-body);
        font-weight: 400;
        padding: 0.5rem 0;
    }
    .site-nav__submenu a:hover {
        background: transparent;
        color: var(--accent);
    }
}

@media (max-width: 480px) {
    .site-header__brand-sub { display: none; }
}