/* ============================================================
   STICKY ANIMATED NAVIGATION
   ============================================================ */

.site-nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background: transparent;
    transition: background-color var(--speed) ease, box-shadow var(--speed) ease,
                backdrop-filter var(--speed) ease;
}
.site-nav.is-scrolled {
    background: var(--nav-bg);
    backdrop-filter: blur(16px) saturate(1.4);
    -webkit-backdrop-filter: blur(16px) saturate(1.4);
    box-shadow: 0 1px 0 var(--line), var(--shadow-sm);
}

.nav-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--sp-4);
    height: 72px;
}

/* ---------- brand ---------- */
.brand {
    display: inline-flex;
    align-items: center;
    gap: 0.65rem;
    text-decoration: none !important;
}
.brand-mark svg { width: 36px; height: 36px; }
.brand-tile { fill: var(--c-primary); transition: fill var(--speed) ease; }
.brand-letter { fill: #fff; }
.brand:hover .brand-tile { fill: var(--c-secondary); }
.brand-name {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.12rem;
    color: var(--text);
    letter-spacing: -0.01em;
}
.brand-thin { font-weight: 500; color: var(--text-muted); }

/* ---------- links ---------- */
.nav-links {
    display: flex;
    align-items: center;
    gap: var(--sp-5);
}
.nav-link {
    position: relative;
    color: var(--text);
    font-weight: 500;
    font-size: var(--fs-300);
    padding-block: 0.4rem;
    text-decoration: none !important;
}
/* sliding underline */
.nav-link::after {
    content: "";
    position: absolute;
    left: 0; bottom: 0;
    width: 100%; height: 2px;
    background: var(--c-primary);
    border-radius: 2px;
    transform: scaleX(0);
    transform-origin: right;
    transition: transform var(--speed) var(--ease-out);
}
.nav-link:hover::after, .nav-link.is-active::after {
    transform: scaleX(1);
    transform-origin: left;
}
.nav-link.is-active { color: var(--c-primary); }
.nav-cta { margin-left: var(--sp-2); }

/* ---------- actions ---------- */
.nav-actions { display: flex; align-items: center; gap: var(--sp-3); }

.theme-toggle {
    width: 40px; height: 40px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--bg-raised);
    color: var(--text);
    transition: transform var(--speed) var(--ease-out), border-color var(--speed) ease;
}
.theme-toggle:hover { transform: rotate(18deg) scale(1.06); border-color: var(--c-primary); }
.theme-toggle svg { width: 19px; height: 19px; fill: none; stroke: currentColor; stroke-width: 1.8; }
.icon-moon { display: none; }
[data-theme="dark"] .icon-moon { display: block; }
[data-theme="dark"] .icon-sun { display: none; }
[data-theme="dark"] .icon-moon path { fill: currentColor; stroke: none; }

/* ---------- burger ---------- */
.nav-burger {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 40px; height: 40px;
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    background: var(--bg-raised);
}
.nav-burger span {
    display: block;
    width: 18px; height: 2px;
    margin-inline: auto;
    background: var(--text);
    border-radius: 2px;
    transition: transform var(--speed) var(--ease-out), opacity var(--speed) ease;
}
.nav-burger[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-burger[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-burger[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- mobile ---------- */
@media (max-width: 767px) {
    .nav-burger { display: flex; }
    .brand-thin { display: none; }

    .nav-links {
        position: fixed;
        inset: 72px 0 auto 0;
        z-index: 99;
        flex-direction: column;
        align-items: stretch;
        gap: 0;
        padding: var(--sp-4) var(--sp-5) var(--sp-6);
        background: var(--nav-bg);
        backdrop-filter: blur(20px) saturate(1.4);
        -webkit-backdrop-filter: blur(20px) saturate(1.4);
        box-shadow: var(--shadow-lg);
        border-bottom: 1px solid var(--line);
        transform: translateY(calc(-100% - 90px)); /* clear the 72px fixed offset + shadow */
        visibility: hidden;
        transition: transform 0.45s var(--ease-out), visibility 0s linear 0.45s;
    }
    .nav-links.is-open {
        transform: translateY(0);
        visibility: visible;
        transition: transform 0.45s var(--ease-out), visibility 0s;
    }
    .nav-link { padding: 0.9rem 0.25rem; font-size: var(--fs-500); border-bottom: 1px solid var(--line); }
    .nav-link::after { display: none; }
    .nav-cta { margin: var(--sp-4) 0 0; justify-content: center; }
}