:root {

    --header-offset: calc(var(--frame-gap, 15px) * 2 + var(--frame-border, 5px));

    --header-blue: #0000FF;
    --header-btn: 44px;
    --menu-width: 260px;

    --layer-header: 1000;
    --layer-note: 900;

    --header-accent: var(--header-blue);
    --header-accent-strong: #1300F3;
    --header-accent-hover: rgba(0, 0, 255, 0.6);
    --header-accent-tint: rgba(0, 39, 255, 0.18);
    --header-accent-tint-strong: rgba(0, 39, 255, 0.28);

    --header-accent-on-panel: #FFFFFF;
}

.logo-container {
    position: fixed;
    top: calc(var(--header-offset) + var(--safe-top, 0px));
    left: calc(var(--header-offset) + var(--safe-left, 0px));
    z-index: var(--layer-header);
    display: flex;
    align-items: center;
    gap: 6px;
    height: var(--header-btn);
}

.logo-link {
    display: block;
    width: var(--header-btn);
    height: var(--header-btn);
    position: relative;
    transition: all 0.3s ease;
}

.logo-link::before {
    content: '';
    position: absolute;
    top: -5px;
    left: -5px;
    right: -5px;
    bottom: -5px;
    border: 3px solid var(--header-accent-strong);
    opacity: 0;
    transition: opacity 0.3s ease;
    pointer-events: none;
}

.logo-link:hover::before { opacity: 1; }
.logo-link:active::before { opacity: 0; }
.logo-link:active:hover::before { opacity: 0; }

.logo-svg {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    filter: hue-rotate(var(--logo-turn, 0deg));
    transition: opacity 0.3s ease, filter 0.6s ease;
}

.logo-clicked { opacity: 0; }
.logo-link:active .logo-svg:not(.logo-clicked) { opacity: 0; }
.logo-link:active .logo-clicked { opacity: 1; }

.logo-container,
.menu-container {
    --header-fade: 320ms;
    --header-shift: -10px;
    --header-lift: 0px;

    opacity: 1;
    visibility: visible;
    transform: translateY(0);
    translate: 0 var(--header-lift);
    transition:
        opacity var(--header-fade) cubic-bezier(0.22, 0.61, 0.36, 1),
        transform var(--header-fade) cubic-bezier(0.22, 0.61, 0.36, 1),
        translate 320ms cubic-bezier(0.22, 0.61, 0.36, 1),
        visibility 0s;
}

.logo-container.header-hidden,
.menu-container.header-hidden {
    opacity: 0;
    visibility: hidden;
    transform: translateY(var(--header-shift));
    pointer-events: none;
    transition:
        opacity var(--header-fade) cubic-bezier(0.4, 0, 0.6, 1),
        transform var(--header-fade) cubic-bezier(0.4, 0, 0.6, 1),
        visibility 0s linear var(--header-fade);
}

[data-header-follow] {
    --header-fade: 320ms;

    opacity: 1;
    visibility: visible;
    transition:
        opacity var(--header-fade) cubic-bezier(0.22, 0.61, 0.36, 1),
        visibility 0s;
}

[data-header-follow].header-hidden {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition:
        opacity var(--header-fade) cubic-bezier(0.4, 0, 0.6, 1),
        visibility 0s linear var(--header-fade);
}

.logo-container.header-compact,
.menu-container.header-compact {
    --header-lift: calc(-1 * (var(--frame-gap, 15px) + var(--frame-border, 5px)));
}

.logo-container.header-instant,
.menu-container.header-instant {
    transition: none;
}

@media (prefers-reduced-motion: reduce) {
    .logo-container,
    .menu-container,
    .logo-container.header-hidden,
    .menu-container.header-hidden {
        transform: none;
        transition: opacity 1ms linear, visibility 0s;
    }
}

.menu-container {
    position: fixed;
    top: calc(var(--header-offset) + var(--safe-top, 0px));
    right: calc(var(--header-offset) + var(--safe-right, 0px));
    z-index: var(--layer-header);
    display: flex;
    align-items: center;
    gap: 0;
}

.menu-button,
.lang-current,
.theme-switch {
    width: var(--header-btn);
    height: var(--header-btn);
    display: flex;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    border-radius: 0;
    padding: 0;
    margin: 0;
    cursor: pointer;
    outline: none;
    color: var(--header-accent);
    transition: all 0.3s ease;
}

.menu-button:hover,
.lang-current:hover,
.theme-switch:hover {
    background: var(--header-accent-hover);
    color: #FFFFFF;
}

.theme-switch:focus-visible {
    outline: 2px solid var(--header-accent);
    outline-offset: -2px;
}

.menu-button.active,
.lang-current.active {
    background: rgba(0, 0, 0, 0.75);
    color: var(--header-accent-on-panel);
}

.menu-icon {
    width: 24px;
    height: 24px;
    color: currentColor;
    transition: color 0.3s ease;
}

.menu-button:hover .menu-icon { color: #FFFFFF; }
.menu-button.active .menu-icon { color: var(--header-accent-on-panel); }

.menu-line {
    transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    transform-origin: center;
}

.globe-icon { width: 22px; height: 22px; }

.theme-icon {
    width: 24px;
    height: 24px;
    color: currentColor;
    transition: transform 0.4s cubic-bezier(0.22, 0.61, 0.36, 1);
}

@media (prefers-reduced-motion: reduce) {
    .theme-icon { transition: none; }
}

.lang-switcher {
    position: relative;
    display: flex;
    align-items: center;
    margin: 0;
    padding: 0;
}

.lang-menu,
.navigation {
    position: absolute;
    top: var(--header-btn);
    right: 0;
    display: none;
    grid-template-columns: 1fr;
    gap: 4px;
    padding: 10px;
    background: rgba(0, 0, 0, 0.75);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: none;
    border-radius: 0;
    box-shadow: none;
    z-index: calc(var(--layer-header) + 1);
}

.lang-menu { width: var(--menu-width); }

.navigation {
    right: 0;
    min-width: var(--menu-width);
}

.lang-menu.open,
.navigation.open { display: grid; }

.lang-item,
.nav-link {
    background: transparent;
    color: #FFFFFF;
    border: none;
    font-family: 'Trebuchet MS', 'Lucida Sans Unicode', 'Lucida Grande', Arial, sans-serif;
    font-size: 18px;
    font-weight: 400;
    letter-spacing: 0.04em;
    padding: 8px 10px;
    border-radius: 0;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    position: relative;
    text-align: left;
    text-decoration: none;
    margin: 0;
}

.lang-item:hover,
.nav-link:hover { background: var(--header-accent-tint); }

.nav-line { display: block; }

.lang-item.active,
.nav-link[aria-current="page"] {
    background: var(--header-accent-tint-strong);
    padding-right: 28px;
}

.lang-item.active::after,
.nav-link[aria-current="page"]::after {
    content: '•';
    position: absolute;
    right: 8px;
    color: #FFFFFF;
    font-weight: bold;
    font-size: 20px;
}

.lang-code {
    font-size: 11px;
    font-weight: 400;
    letter-spacing: 0.08em;
    opacity: 0.45;
}

.lang-item.active .lang-code { opacity: 0.8; }

.nav-subtitle {
    color: rgba(255, 255, 255, 0.6);
    font-size: 10px;
    font-weight: 400;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin: 8px 0 4px 0;
    padding: 0 10px;
}

.nav-subtitle:first-child { margin-top: 0; }

.nav-link-disabled {
    opacity: 0.5;
    cursor: not-allowed;
    pointer-events: none;
}

.nav-superscript {
    font-style: italic;
    font-size: 0.7em;
    vertical-align: super;
}

@media (max-width: 768px) {
    :root {
        --header-btn: 40px;
        --menu-width: 230px;
    }

    .lang-item,
    .nav-link { font-size: 16px; }
}

@media (max-width: 480px) {
    :root {
        --header-btn: 36px;
        --menu-width: 210px;
    }

    .globe-icon { width: 18px; height: 18px; }
    .menu-icon { width: 20px; height: 20px; }

    .theme-icon { width: 20px; height: 20px; }

    .lang-menu,
    .navigation { padding: 8px; }

    .lang-item,
    .nav-link { font-size: 15px; padding: 6px 8px; }

    .lang-item.active,
    .nav-link[aria-current="page"] { padding-right: 26px; }

    .nav-subtitle { font-size: 9px; margin: 6px 0 3px 0; padding: 0 8px; }
}

.seo-nav,
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    margin: -1px;
    padding: 0;
    overflow: hidden;
    clip: rect(0 0 0 0);
    clip-path: inset(50%);
    white-space: nowrap;
    border: 0;
}