/* =========================================================
   Sticky top navigation with backdrop blur.
   Collapses to a hamburger menu below 700px.
   ========================================================= */

.site-nav {
    position: sticky;
    top: 0;
    z-index: 1000;
    width: 100%;
    background: rgba(247, 251, 255, 0.72);
    -webkit-backdrop-filter: saturate(160%) blur(14px);
    backdrop-filter: saturate(160%) blur(14px);
    border-bottom: 1px solid var(--border-soft);
    transition: background var(--dur) var(--ease),
                border-color var(--dur) var(--ease);
}

/* When the viewport has scrolled past the hero the nav adopts a
   subtly darker tint so it reads against the underwater sections. */
.site-nav.is-scrolled {
    background: rgba(1, 26, 51, 0.78);
    border-bottom-color: rgba(234, 243, 255, 0.08);
    color: var(--on-dark);
}

.site-nav.is-scrolled .nav-link {
    color: var(--on-dark-muted);
}

.site-nav.is-scrolled .nav-link:hover,
.site-nav.is-scrolled .nav-link:focus-visible,
.site-nav.is-scrolled .nav-link.is-active {
    color: var(--accent);
}

.site-nav.is-scrolled .brand-text {
    color: var(--on-dark);
}

.site-nav.is-scrolled .brand-mark {
    color: var(--accent);
}

.nav-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1.5rem;
    max-width: var(--content-max);
    margin-inline: auto;
    padding: 0.85rem var(--gutter);
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    font-family: var(--font-mono);
    font-weight: 700;
    font-size: 0.95rem;
    letter-spacing: 0.02em;
    color: var(--ink);
}

.brand-mark {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    color: var(--wave);
}

.brand-mark svg {
    width: 100%;
    height: 100%;
}

.brand-text {
    color: var(--ink);
    transition: color var(--dur) var(--ease);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 1.6rem;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-link {
    position: relative;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--ink-muted);
    transition: color var(--dur) var(--ease);
}

.nav-link::after {
    content: '';
    position: absolute;
    left: 0;
    right: 100%;
    bottom: -6px;
    height: 2px;
    background: currentColor;
    transition: right var(--dur) var(--ease);
}

.nav-link:hover,
.nav-link:focus-visible,
.nav-link.is-active {
    color: var(--wave-darker);
}

.nav-link:hover::after,
.nav-link:focus-visible::after,
.nav-link.is-active::after {
    right: 0;
}

.nav-cta {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.55rem 1rem;
    border-radius: 999px;
    background: var(--ink);
    color: var(--sky);
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 500;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    transition: transform var(--dur) var(--ease),
                background var(--dur) var(--ease);
}

.nav-cta:hover,
.nav-cta:focus-visible {
    background: var(--wave-darker);
    transform: translateY(-1px);
}

.site-nav.is-scrolled .nav-cta {
    background: var(--accent);
    color: var(--abyss);
}

.site-nav.is-scrolled .nav-cta:hover,
.site-nav.is-scrolled .nav-cta:focus-visible {
    background: var(--on-dark);
}

/* Hamburger toggle (hidden on desktop) */
.nav-toggle {
    display: none;
    background: transparent;
    border: 0;
    padding: 0.5rem;
    cursor: pointer;
    color: inherit;
}

.nav-toggle-icon,
.nav-toggle-icon::before,
.nav-toggle-icon::after {
    display: block;
    width: 22px;
    height: 2px;
    background: currentColor;
    border-radius: 2px;
    transition: transform var(--dur) var(--ease),
                opacity var(--dur) var(--ease);
}

.nav-toggle-icon {
    position: relative;
}

.nav-toggle-icon::before,
.nav-toggle-icon::after {
    content: '';
    position: absolute;
    left: 0;
}

.nav-toggle-icon::before { top: -7px; }
.nav-toggle-icon::after  { top:  7px; }

.nav-toggle[aria-expanded='true'] .nav-toggle-icon {
    background: transparent;
}

.nav-toggle[aria-expanded='true'] .nav-toggle-icon::before {
    top: 0;
    transform: rotate(45deg);
}

.nav-toggle[aria-expanded='true'] .nav-toggle-icon::after {
    top: 0;
    transform: rotate(-45deg);
}

@media (max-width: 780px) {
    .nav-toggle {
        display: inline-flex;
        align-items: center;
        justify-content: center;
    }

    .nav-cta {
        display: none;
    }

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        display: grid;
        gap: 0;
        background: rgba(1, 26, 51, 0.95);
        -webkit-backdrop-filter: blur(14px);
        backdrop-filter: blur(14px);
        border-bottom: 1px solid rgba(234, 243, 255, 0.08);
        padding: 0.5rem 0;
        transform-origin: top;
        transform: scaleY(0);
        opacity: 0;
        pointer-events: none;
        transition: transform var(--dur) var(--ease),
                    opacity var(--dur) var(--ease);
    }

    .nav-menu.is-open {
        transform: scaleY(1);
        opacity: 1;
        pointer-events: auto;
    }

    .nav-links {
        flex-direction: column;
        align-items: stretch;
        gap: 0;
    }

    .nav-link {
        padding: 0.9rem var(--gutter);
        color: var(--on-dark-muted);
    }

    .nav-link::after {
        display: none;
    }

    .nav-link:hover,
    .nav-link:focus-visible,
    .nav-link.is-active {
        background: rgba(127, 211, 255, 0.08);
        color: var(--accent);
    }
}